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CBSE Sample Papers for Class 12 Physics Paper 7 are part of CBSE Sample Papers for Class 12 Physics. Here we have given CBSE Sample Papers for Class 12 Physics Paper 7.

CBSE Sample Papers for Class 12 Physics Paper 7

Time Allowed : 3 Hours

Max. Marks : 70

General Instructions 

• All questions are compulsory. There are 26 questions in all.
• This question paper has five sections: Section A, Section B, Section C, Section D and Section E.
• Section A contains five questions of 1 mark each. Section B contains five questions of 2 marks each. Section C contains twelve questions of 3 marks each. Section D contains one value based question of 4 marks and Section E contains three questions of 5 marks each.
• There is no overall choice. However, an internal choice has been provided in 1 question of 2 marks, 1 question of 3 marks and all the 3 questions of 5 marks weightage. You have to attempt only 1 of the choices in such questions.
• You may use the following values of physical constants wherever necessary :

Questions
SECTION : A

Question 1.
What is the range of frequencies used in satellite communication? What is common between these waves and light waves?

Question 2.
Define capacitor reactance. Write its S.I. units.

Question 3.
A concave lens of refractive index 1.5 is immersed in a medium of refractive index 1.65. What is the nature of the lens ?

Question 4.
What is the electric flux through a cube of side 1 cm which encloses an electric dipole?

Question 5.
Graph showing the variation of current versus voltage for a material GaAs is shown in the figure, Identify the region of :

1. negative resistance
2. where Ohm’s law is obeyed.

SECTION : B

Question 6.
Name the parts of the electromagnetic spectrum which is

1. suitable for radar systems used in aircraft navigation
2. used to treat muscular strain
3. used as a diagnostic tool in medicine

Write in brief, how these waves can be produced.

Question 7.
Distinguish between ‘intrinsic’ and ‘extrinsic’ semiconductors.

Question 8.
Show that the radius of the orbit in hydrogen atom varies as n², where n is the principal quantum number of the atom.

Question 9.
Use the mirror equation to show that an object placed between f and 2f of a concave mirror produces a real image beyond 2 f.

OR

Find an expression for intensity of transmitted light when a Polaroid sheet is rotated between two crossed Polaroids. In which position of the Polaroid sheet will the transmitted intensity be maximum ?

Question 10.
A proton and an a-particle have the same de Broglie wavelength. Determine the ratio of
(i) their accelerating potentials
(ii) their speeds.

SECTION : C

Question 11.
State the principle of working of a galvanometer. A galvanometer of resistance G is converted into a voltmeter to measure up to V volts by connecting a resistance R₁ in series with the coil. If a resistance R₂ is connected in series with it, then it can measure up to V/2 volts. Find the resistance, in terms of R₁ and R₂, required to be connected to convert it into a voltmeter that can read up to 2 V. Also find the resistance G of the galvanometer in terms of R₁ and R₂.

Question 12.
Two capacitors of unknown capacitance C₁ and C₂ are connected first in series and then in parallel across a battery of 100 V. If the energy stored in the two combinations is 0.045 J and 0.25 J respectively, determine the value of Cj and C₂. Also calculate the charge on each capacitor in parallel combination.

Question 13.
With what considerations in view, a photo diode is fabricated ? State its working with the help of a suitable diagram. Even though the current in the forward bias is known to be more than in the reverse bias, yet the photo diode works in reverse bias. What is the reason ?

Question 14.
(a) Write Einstein’s photoelectric equation and mention which important features in photoelectric effect can be explained with the help of this equation.
(b) The maximum kinetic energy of the photo electrons gets doubled when the wavelength of light incident on the surface changes from λ₁ to λ₂. Derive the expressions for the threshold wavelength X₀ and work function for the metal surface.

Question 15.
LFse Kirchhoff’s rules to obtain conditions for the balance condition in a Wheatstone bridge.

Question 16.
In the study of Geiger-Marsdan experiment on scattering of α-particles by a thin foil of gold, draw the trajectory of α-particles in the Coulomb field of target nucleus.
Explain briefly how one gets the information on the size of the nucleus from this study. From the relation R = R₀ A^1/3, where R₍₎ is constant and A is the mass number of the nucleus, show that nuclear matter density is independent of A.

OR

Distinguish between nuclear fission and fusion. Show how in both these processes energy is released. Calculate the energy release in MeV in the deuterium-tritium fusion reaction :

Question 17.
A cell of emf ‘E’ and internal resistance V is connected across a variable load resistor R. Draw the plots of the terminal voltage V versus
(i) R and
(ii) the current I. It is found that when R = 4 Ω, the current is 1A and when R is increased to 9 Ω, the current reduces to 0.5 A. Find the values of the emf E and internal resistance r.

Question 18.
An inductor L of inductance X_L is connected in series with a bulb B and an ac source. How would brightness of the bulb change when

1. number of turn in the inductor is reduced,
2.  an iron rod is inserted in the inductor and
3. a capacitor of reactance X_c = X_L is inserted in series in the circuit. Justify your answer in each case.

Question 19.
Draw a block diagram of a detector for AM signal and show, using necessary processes and the wave forms, how the original message signal is detected from the input AM wave.

Question 20.
Draw a circuit diagram of a transistor amplifier in CE configuration. Define the terms :
(i) Input resistance and
(ii) Current amplification factor.
How are these determined using typical input and output characteristics ?

Question 21.
Answer the following questions :
(a) In a double slit experiment using light of wavelength 600 nm, the angular width of the fringe formed on a distant screen is 0.1°. Find the spacing between the two slits.
(b) Light of wavelength 5000 Å propagating in air gets partly reflected from the surface of water. How will the wavelengths and frequencies of the reflected and refracted light be affected?

Question 22.
(i) A giant refracting telescope has an objective lens of focal length 15 m. If an eyepiece of focal length 1.0 cm is used. What is the angular magnification of the telescope ?
(ii) If this telescope is used to view the moon. What is the diameter of the image of the moon formed by the objective lens ? The diameter of the moon is 3.48 x 10⁸ m and the radius of lunar orbit is 3.8 x 10⁸ cm.

SECTION : D

Question 23.
A group of students while coming from the school noticed a box marked “Danger H.T. 2200 V” at a substation in the main street. They did not understand the utility of a such a high voltage, while they argued the supply was only 220 V. They asked their teacher this question the next day. The teacher thought it to be an important question and therefore, explained to the whole class. Answer the following questions :

1. What device is used to bring the high voltage down to low voltage of a.c. current and what is the principle of its working ?
2. Is it possible to use this device for bringing down the high dc voltage to the low voltage? Explain.
3. Write the values displayed by the students and the teacher. 4

SECTION : E

Question 24.
(a) An electric dipole of dipole moment P consists of point charges +q and -q separated by a distance 2a apart. Deduce the expression for the electric field E due to the dipole at a distance x from the centre of the dipole on its axial line in terms of the dipole moment P Hence show that in the limit

(b) Given the electric field in the region E = 2×1, find the net electric flux through the cube and the charge enclosed by it.

OR

(a) Explain using suitable diagrams, the difference in the behaviour of a
(i) conductor and
(ii) dielectric in the presence of external electric field. Define the terms polarization of a dielectric and write its relation with susceptibility.
(b) A thin metallic spherical shell of radius carries a charge Q on its surface. A point charge Q/2 is placed at its centre C and another charge +2Q is placed outside the shell at a distance x from the centre as shown in the figure.
Find
(i) the force on the charge at the centre of shell and at the point A,
(ii) the electric flux through the shell.

Question 25.

(a) A point object ‘O’ is kept in a medium of refractive index n₁ in front of a convex spherical surface of radius of curvature R which separate the second medium of refractive index n₂ from the first one as shown in the figure. Draw the ray diagram showing the image formation and deduce the relationship between the object distance and the image distance in terms of n₁ n₂ and R.
(b) When the image formed above acts as a virtual object for a concave spherical surface separating the medium n₂ from n₁ (n₂> n₁) draw this ray diagram and write the similar (similar to (a)) relation. Hence obtain the expression for the Lens Makers formula.

OR

(a) What is polarisation of light? Under what condition does a beam of light reflected by a transparent medium becomes plane polarised? Use the condition to establish a relation between the angle of incidence and the refractive index of the transparent medium.
(b) State the essential condition for Rayleigh scattering to occur.
(c) Compare the intensity of scattering of light of wavelength 400 nm and 600 nm in the earth’s atmosphere.

Question 26.

(a) State Ampere’s Circuital law. Use this law to obtain the expression for the magnetic field inside an air cored toroid of average radius, having V turns per unit length and carrying a steady current I.
(b) An observer to the left of a solenoid of N turns each of cross section area A observes that a steady current I in it flows in the clockwise direction. Depict the magnetic field lines due to the solenoid specifying its polarity and show that it acts as a bar magnet of magnetic momentum M = NIA.

OR

(a) Define mutual inductance and write its S.I. units.
(b) Derive an expression for the mutual inductance of two long co-axial solenoids of same length wound one over the other.
(c) In an experiment two coils c₁, and c₂ are placed close to each other. Find out the expression for the emf induced in the coil c₁ due to a change in the current through the coil c₂.

Answers
SECTION : A

Answer 1.
Range of frequencies used in satellite communication is

1. Uplink = 5.925 – 6.425 GHz
2. Downlink = 3.7 – 4.2 GHz
3. Both space waves and light waves are electromagnetic.

Answer 2.
Capacitor reactance is the resistance offered by a capacitor to the flow of a.c. It is given by

Where co (Angular frequency of the source) = 2nf;
f = frequency of the source

C = Capacitance of the capacitor

Answer 3.
Since μ_g lens < μ_m surroundings. It behaves like a converging lens.

Answer 4.
The electric flux through a cube of side 1 cm which encloses an electric dipole will be zero, as net charge enclosed by a cube is zero.

Answer 5.

1. DE is the region of negative resistance because the slope of curve in this part is negative.
2. BC is the region where Ohm’s law is obeyed because in this part, the current varies linearly with the voltage.
   

SECTION : B

Answer 6.

1. Microwaves are suitable for radar systems that are used in aircraft navigation. These rays are produced by special vacuum tubes, namely -klystrons, magnetrons and Gunn diodes.
2. Infrared waves are used to treat muscular strain. These rays are produced by hot bodies and molecules.
3. X-rays are used as a diagnostic tool in medicine. These rays are produced when high energy electrons are stopped suddenly on a metal of high atomic number.

Answer 7.

Answer 8.
According to the Bohr’s theory of hydrogen atom, the angular momentum of a revolving electron is given by

Here,
m = Mass of the electron
v = Velocity of the electron
r = Radius of the orbit
h = Planck’s constant
n = Principal quantum number
If an electron of mass m and velocity v is moving in a circular orbit of radius r, then the centripetal force required is given by

Also, if the charge on the nucleus is Ze, then the force of electrostatic attraction between the nucleus and the electron will provide the necessary centripetal force.

Answer 9.
Mirror equation is

Where u is distance of object from the mirror, v is the distance of image from the mirror and f is the focal length of the mirror.
For a concave mirror/is negative i.e.,f < 0,u < 0 For a real object (on the left of mirror)


This implies that v is negative and greater than 2f This means that the image lies beyond 2f and it is real.

Let us consider two crossed polarisers P₁ and P₂ with a polaroid sheet P₃ placed between them. Let I_Q be the intensity of polarized light after passing through the first polarizer P₁. If 0 is the angle between the axes of P₁ and P₂ then the intensity of the polarized light after passing through P₃ will be I = I₀ cos² θ.
As P₁ and P₂ are crossed, the angle between the axes of P₁ and P₂ = 90°.
∴  Angle between the axes of P₂ and P₃ = (90° – θ)

Answer 10.
(i) The de Broglie wavelength of a particle is given by

where, V is the accelerating potential of the particle
It is given that
λ_proton  =  λ_alpha

(ii) We can also write de Broglie wavelength as λ = h/mv  where h is Planck’s constant, m is mass of the particle and v is speed of the particle.

SECTION : C

Answer 11.
Principle :
When a current-carrying coil is placed in a magnetic field, it experiences a torque. From the measurement of the deflection of the coil, the strength of the current can be computed. A high resistance is connected in series with the galvanometer to convert it into voltmeter. The value of the resistance is given by

Here,
V = Potential difference across the terminals of the voltmeter
I_g  = Current through the galvanometer
G = Resistance of the galvanometer
When the resistance R₁, is connected in series with the galvanometer,
V = I (G + R₁)
When the resistance R₁ is connected in series with the galvanometer,

Let R₃ be the resistance required for conversion into voltmeter of range 2V
∴  2 V = I_g (G + R₃)
Also
V = I_g(G + R₁)

Answer 12.
When the capacitors are connected in parallel. Equivalent capacitance, C_p = C₁+ C₂ The energy stored in the combination of the capacitors,

When the capacitors are connected in parallel, the charge on each of them can be obtained as follows:
Q₁ = C₁V = 38.2 x 10^-6 x loo = 38.2 x 10^-4 C
Q₂ = C₂V= 11.8 x x 10^-6 x 100= 11.8 x x 10^-4 C

Answer 13.
A photo diode is used to observe the change in current with change in the light intensity under reverse bias condition. In fabrication of photo diode, material chosen should have band gap -1.5 eV or lower so that solar conversion efficiency is better. This is the reason to choose Si or GaAs material. Working: It is a p-n junction fabricated with a transparent window to allow light photons to fall on it. These photons generate electron hole pairs upon absorption. If the junction is reverse biased using an electrical circuit, these electron hole pair move in opposite directions so as to produce current in the circuit. This current is very small and is detected by the micro ammeter placed in the circuit.

A photo diode is preferably operated in reverse bias condition. Consider an «-type semiconductor. Its majority carrier (electron) density is much larger than the minority hole density. When illuminated with light, both types of carriers increase equally in number

That is, the fractional increase in majority carriers is much less than the fractional increase in minority carriers. Consequently, the fractional change due to the photo-effects on the minority carriers dominated reverse bias current is more easily measurable than the fractional change in the majority carrier dominated forward bias current. Hence, photo diodes are preferably used in the reverse bias condition for measuring light intensity.

Answer 14.
(a) Einstein’s photoelectric equations is given by

Where
K_max ⁼ Maximum kinetic energy of the photoelectron
^vmax ⁼ Maximum velocity of the emitted photoelectron
m = Mass of the photoelectron
v = Frequency of the light radiation
Φ₀ = Work function h = Planck’s constant
If v_o is the threshold frequency, then the work function can be written as

The above equations explains the following results.

1. If v < v_o, then the maximum kinetic energy is negative, which is impossible. Hence, photoelectric emission does not take place for the incident radiation below the threshold frequency. Thus, the photoelectric emission can take place only if
   v > v_o.
2. The maximum kinetic energy of emitted photo electrons is directly proportional to the frequency of the incident radiation. This means that maximum kinetic energy of photo electron depends only on the frequency of incident light.

(b) According to the photoelectric equation,

Answer 15.
Let us consider a Wheatstone bridge arrangement as shown below :
Wheatstone bridge is a special bridge type circuit which consists of four resistances, a galvanometer and a battery. It is used to determine unknown resistance. In figure four resistance P, Q, R and S are connected in the form of four arms of a quadrilateral. Let the current given by battery in the balanced position be I. This current on reaching point A is divided into two parts I₁ and I₂. As there is no current in galvanometer in balanced state, therefore current in resistances P and Q is I₁ and in resistances R and S it is I₁.


This is condition of balanced Wheatstone bridge

Answer 16.
From this experiment, the following is observed :

1. Most of the alpha particles pass straight through the gold foil. It means that they do not suffer any collision with gold atoms.
2. About one alpha particle in every 8000 alpha particles deflects by more than 90°. As most of the alpha particles go undeflected and only a few get deflected, this shows that most of the space in an atom is empty and at the centre of the atom, there exists a nucleus. By the number of the alpha particles deflected, the information regarding size of the nucleus can be known.

If m is the average mass of a nucleon and R is the nuclear radius, then mass of nucleus = mA, where A is the mass number of the element. This shows that the nuclear density is independent of A.

OR

Nuclear fission :
Nuclear fission is a disintegration process, in which a heavier nucleus gets split up into two lighter nuclei, with the release of a large amount of energy.

Answer 17.

Answer 18.

1. When the number of turns in the inductor is reduced, its reactance X_L decreases. The current in the circuit increases and hence brightness of the bulb increases.
2. When an iron rod is inserted in the inductor, the self inductance increases. Consequently, the inductive reactance X_L = coL increases. This decreases the current in the circuit and the bulb glows dimmer.
3. With capacitor of reactance X_c = X_L, the impedance
   
   becomes minimum, the current in circuit becomes maximum. Hence the bulb glows with maximum brightness.

Answer 19.

When a message is received, it gets attenuated through the channel therefore, receiving antenna is to be followed by an amplifier and a detector. The signal frequency is usually changed to a lower frequency in an Intermediate Frequency (IF) stage. The detected signal may not be strong enough to be made use of and hence is required to be amplified. In order to obtain the original message signal m(t) of angular frequency a simple method is used which is shown in the form of a block diagram.

When the received modulated signal is passed through a rectifier, an envelope signal is produced. This envelope signal is the message signal. In order to retrieve the message, the signal is passed through an envelope detector.

Answer 20.

Answer 21.
(a) Angular width (0) of fringe in double-slit experiment is given by 0 = λ/d
Where, d = Spacing between the slits
Given, Wavelength of light, X = 600 nm
Angular width of fringe,

(b) The frequency and wavelength of reflected wave will not change. The refracted wave will have same frequency, only wavelength will change. The velocity of light in water is given by v = λf
where,
v = Velocity of light
f= Frequency of light
λ = Wavelength of light
As light ray is travelling from rarer (air) medium to denser medium, its speed will decrease. Hence, wavelength (λ) will also decrease.

Answer 22.
(i) Let
f₀ = Focal length of the objective lens = 15 m = 1500 cm
f_e = Focal length of the eye lens = 1.0 cm
Angular magnification of the giant refracting telescope is given by

(ii) Diameter of the image of the moon formed by the objective lens, d = αf_o

SECTION : D

Answer 23.

1. The device that is used to bring high voltage down to low voltage of an a.c. current is a transformer. It works on the principle of mutual induction of two windings or circuits. When current in one circuit changes, emf is induced in the neighbouring circuit.
2. The transformer cannot convert d.c. voltages because it works on the principle of mutual induction. When the current linked with the primary coil changes, the magnetic flux linked with the secondary coil also changes. This change in flux induces emf in the secondary coil. If we apply a direct current to the primary coil the current will remain constant. Thus, there is no mutual induction and hence no emf is induced.
3. The value of gaining knowledge and curiosity about learning new things is being displayed by the students. The value of providing good education and undertaking the doubts of students has been displayed by the teacher.

SECTION : E

Answer 24.
(a) Electric field at a point on the axial line

(b) Since, the electric field is parallel to the faces, parallel to xy and xz planes, the electric flux through them is zero.
Electric flux through the left face

OR

(a) (i) Conductor :
E₀ → external field
E_m → internal field created by the redistribution of electrons inside the metal.
When a conductor like a metal is subjected to external electric field, the electrons experience a force in the opposite direction collecting on the left hand side. A positive charge is therefore induced on the right hand side. This creates an opposite electric field (E_m) that balances out (E₀).

∴ The net electric field inside the conductor becomes zero.

(ii) Dielectric :
When external electric field is applied, dipoles are created (in case of non-polar dielectrics). The placement of dipoles is as shown in the given figure. An internal electric field is created which reduces the external electric field.  Polarization of dielectric (P) is defined as the dipole moment per unit volume of the polarized dielectric.

^p = X_es₀ E
X_e = susceptibility
E = Electric field

Answer 25.
(a) Let a spherical surface separate a rarer medium of refractive index n₁ from denser medium of refractive index n₂. Let C be the centre of curvature and R = MC be the radius of the surface.

Consider a point object O lying on the principal axis of the surface. Let a ray starting from O incident normally on the surface along OM and pass straight. Let another ray of light incident on NM along ON and refract along NI. From M, draw MN perpendicular to 01.

The figure shows the geometry of formation of image I of an object O and the principal axis of a spherical surface with centre of curvature C and radius of curvature R.
Let us make the following assumptions :

1. The aperture of the surface is small as compared to the other distance involved.
2. NM will be taken as nearly equal to the length of the perpendicular from the point N on the principal axis.

OR

(a) Restricting the vibrations of electric vector (light) in a single direction perpendicular to the direction of propagation of light is called polarisation of light. At polarising angle refracted and reflected components of light are perpendicular to each other. In fig.

Answer 26.
(a) Amperes circuital law in electro magnetism is analogous to Gauss law in electrostatics. This law states that “The line integral of resultant magnetic field along a closed plane curve is equal to p₀ time the total current crossing the area bounded by the closed curve provided the electric field inside the loop remains constant. Thus ƒ B .dl = μ.₀I_enc, where p₀ is permeability of free space and I_enc is the net current enclosed by the loop.

A toroid is a hollow circular ring on which a large number of turns of a wire are closely wound. Consider an air-cored toroid (as shown here) with centre O.
Given,
r = Average radius of the toroid
I = Current through the solenoid .
n = Number of turns per unit length

To determine the magnetic field inside the toroid, we consider three amperian loops (loop 1, loop 2 and loop 3) as show in the figure below.

This is the expression for magnetic field inside air-cored toroid.
(b) Given that the current flows in the clockwise direction for an observer on the left side of the solenoid. This means that left face of the solenoid acts as south pole and right face acts as north pole. Inside a bar magnet the magnetic field lines are directed from south to north. Therefore, the magnetic field lines are directed from left to right in the solenoid. Magnetic moment of single current carrying loop is given by
m = IA
where
I = Current flowing through the loop;
A = Area of the loop So, Magnetic moment of the whole solenoid is given by
M = Nm = N(IA)

OR

(a) Mutual inductance is the property of two coils by the virtue of which each opposes any change in the value of current flowing through the other by developing an induced emf. The SI unit of mutual inductance is henry and its symbol is H.
(b) Consider two long solenoids S₁ and S₂ of same length / such that solenoid S₂ surrounds
solenoid S, completely.

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CBSE Sample Papers for Class 12 Physical Education Paper 2 are part of CBSE Sample Papers for Class 12 Physical Education. Here we have given CBSE Sample Papers for Class 12 Physical Education Paper 2.

CBSE Sample Papers for Class 12 Physical Education Paper 2

Students who are going to appear for CBSE Class 12 Examinations are advised to practice the CBSE sample papers given here which is designed as per the latest Syllabus and marking scheme as prescribed by the CBSE is given here. Paper 2 of Solved CBSE Sample Paper for Class 12 Physical Education is given below with free PDF download solutions.

Time: 3 Hours
Maximum Marks: 70

General Instructions:

• All questions are compulsory.
• Answers to questions carrying 1 mark should approximately 10-20 words.
• Answers to questions carrying 3 marks should approximately 30-50 words.
• Answers to questions carrying 5 marks should approximately 75-100 words.

Questions.

Question 1.
Define Strength? 1

Question 2.
Define personality? 1

Question 3.
What do you understand by Friction in Sports? 1

Question 4.
Define Fracture? 1

Question 5.
Define Cardiac Output? 1

Question 6.
Define Yoga? 1

Question 7.
Define Good Posture? 1

Question 8.
Enlist types of disorders and disabilities among children? 1

Question 9.
Define Axis and Plain? 1

Question 10.
Indicate the formula used for ‘BYE’ in knock-out tournament? 1

Question 11.
Define Aggression? 3

Question 12.
Describe the objectives of Intramural Competition in institutions? 1

Question 13.
Describe Newton’s law of motion used in sports? 3

Question 14.
Explain micro and macro nutrients? 3

Question 15.
Elaborate reasons for mal posture? 3

Question 16.
Explain factors effecting motor development? 3

Question 17.
The school has proposed to organize sports activities for its school children. The sports committee was formed and it proposed for an inter house sports competitions. All the children of the school have been divided into various houses and designated with different colours to differentiate. 3
(i) Which type of competition is being discussed for school children?
(ii) What are the various committees required for organization of the competitions?
(iii) What are the benefits of organizing such sports competition?

Question 18.
List Different types of fractures? 3

Question 19.
Draw a fixture of 9 Football teams participating in a Tournament on the basis of knock? 3

Question 20.
Explain the role of sports in development of personality? 5

Question 21.
Explain the role of nutrition on sports performance? Describe the essential nutrients influencing sports performance? 5

Question 22.
Describe the concept of PRICE used for injury management? 5

Question 23.
Explain the effect of exercise on Cardiovascular system? 5

Question 24.
Describe Trajectory? Explain the factors affecting projectile trajectory? 5

Question 25.
Illustrate AAPHER motor fitness test? 5

Question 26.
Appraise the role of physical activity for maintaining functional fitness among elderly people? 5

Answers.

Answer 1.
Strength is the ability of the muscle to overcome resistance. It is the amount of force a muscle or muscle groups can exert. It is achieved by voluntary muscle contraction. Specified types of strength is required for different types of activity, exercise and sports.

Answer 2.
Personality is the unique and relatively stable pattern of behaviour, thoughts and feelings of an individual. It is derived from the latin word ‘persona’ meaning ‘mask’. Personality is described as sum total of all traits and distinguishing qualities of an individual.

Answer 3.
The action of one surface or object rubbing against another. It is the resistance that one surface or object encounters when moving over another.

Answer 4.
Fracture is any discontinuation in bone due to any trauma. It can be a complete or incomplete break in a bone resulting from the application of excessive force. A fracture usually results from traumatic injury to bones causing the continuity of bone tissues or bony cartilage to bedisrupted or broken.

Answer 5.
Cardiac output is the effective volume of blood expelled by either ventricle of the heart per unit of time (generally per minute); it usually refers to left ventricle output. It is equal to the stroke volume multiplied by the heart rate. Normal values are 4 to 8 liters per minute.

Answer 6.
Yoga is a science of balancing between mind, body and spirit. It is derived from the Sanskrit word ‘Yuj’in spiritual terms mean the union of the individual consciousness with the universal consciousness.

Answer 7.
“Good posture is applied to right position of the body assumed while doing any action so that minimum energy is consumed in order to get maximum efficiency.

Answer 8.
Disorders:  ADHD, SPD, ODD, Down syndrome, cerebral palsy, learning disorder.
Disability:  Physical, Cognitive, Intellectual, Adaptive.

Answer 9.
An axis is a straight line around which an object rotates.
Plane is the surface on which movement takes place.

Answer 10.
Formula for giving Bye = Next power of 2 – No. of Teams

Answer 11.
Aggression is defined as any form of behaviors directed towards the goal of or injuring another living being who is motivated to avoid such treatment.

Answer 12.
Objective of Intramurals:

• Promote physical, mental, social and emotional development of students.
• Create health awareness and promote well being.
• Inculcate Values and Ethics among students.
• Provide opportunity to every student to participate in sports.
• Develop leadership qualities.
• Develop group cohesion
• Provide recreation
• Facilitate talent identification and development
• Provide opportunity to experience sports environment

Answer 13.

The Law of Inertia: A body at rest tends to remain at rest. A body in motion tends to continue in motion with consistent speed and in the same direction unless acted upon by an outside force. Example is the most anything in the real world—gravity, the surface of the playing field, a defensive player, or the braking action of an athlete’s body to stop.

The Law of Acceleration: The velocity of a body is changed only when acted upon by an additional force. The produced acceleration or deceleration is proportional to and in the same direction of the force. If a baseball player hits a ball with double the force, the rate at which the ball will accelerate (speed up) will be doubled. Football players can slow down, stop, or reverse the direction of other players depending upon how much force they can generate and in which direction.

The Law of Counterforce: The production of any force will create another force opposite and equal to the first force. A swimmer propels herself through the water because the water offers enough counterforce to oppose the action of her hands pushing, allowing her to move. An athlete can jump higher off a solid surface because it opposes his body with as much force as he is able to generate, in contrast to sand or other unstable surface.

Answer 14.
Nutrients are environmental substances used for energy, growth and bodily functions by organisms. Depending as the nutrient, these substances are needed is small amounts or larges amounts. Those that are needed in large amounts are called Macronutrients.

Micronutrients: as opposed to Macronutients. (protein, carbohydrates and fat), are comprised of vitamins and minerals which are required in small quantities to ensure normal metabolism, growth and physical well-being.
Minerals can be classified as macro minerals like calcium, potassium, sodium, magnesium, phosphorous and micro mineral (like iodine, iron, chromium, etc.)
Vitamins can be soluble like Vitamin A, D, E, etc.) or water soluble (like Vitamin B complex, B2, B3 etc.)

Answer 15.
Mal-posture means faulty carriage or incorrect alignment of different parts of body in respect to each other. It occurs due to the following reasons.

• Muscular weakness
• Malnourishment
• Faulty desks and seats
• Defective eye-sight or hearing
• Improper exercises
• Typical occupations
• Too rapid growth during adolescence
• Carrying weights
• Use of improper belonging
• Poor posture of teachers
• Heredity and environments

Answer 16.
Growth of the child: As children grow and learn, their ability to perform more activities with their body and understand actions improves. This can be affected by age and size. While most motor development skills have age-specific target ranges, the skills are also influenced by children being small or tall for their age, their weight, and their mental development.

Environment: The child’s environment has a large effect on their motor skill development. The more opportunities they have to develop both gross and fine motor skills, the faster their capacity increases. For instance, if a child is encouraged to play outside on park equipment or other areas where they can climb, run, and play, their gross motor skills will develop quickly. Additionally, fine motor skills increase when children are encouraged to play with their hands, hold and touch smaller items, feed themselves, and draw or color.

Genetics: Children are affected both by the genetics of their parents and their own genetics. If there are genetic weaknesses, they may have slower motor skill development than general guidelines suggest for their age range. For instance, if a child has weak muscle tone or health issues, they will likely develop at a slower pace than other healthy children of their age.

Muscle Tone: As mentioned previously, muscle tone can affect motor skills. The stronger a child is, the more ability they may have to move and control their body. Muscles are a fundamental factor in a child having the strength to move their body and control their actions. If muscle development is weak, their motor skill development will be slower.

Gender: Gender plays an important role in how children develop. Boys often have more advanced motor skills than girls because they are typically stronger and more aggressive physically. At the same time, girls often have more advanced eye and hand coordination. They may be more able to balance fine motor skills and gross motor skills, using both large movements and more detailed actions interchangeably.

Answer 17.
(i) Intramural Competition
(ii) Committee:

• Technical Committee
• Financial Committee
• Refreshment committee
• Ceremonial Committee
• Logistics Committee
• Record and Certificate Committee
• Jury of Appeal Committee

(iii) Importance:

• Motto is towards maximum participation
• Develop Group Cohesion
• Physical, Mental, Emotional, Social Development
• Recreation
• Psychomotor development

Answer 18.
Types of Fracture:
(i) Close Fracture:

• Transverse Fracture: Broken at right angle to long axis of bone
• Oblique: Oblique direction to long axis, confined to one plane .A fracture in which the line of break runs obliquely to the axis of the bone.
• Spiral Fracture: Occur when one end of an extremity is fixed (e.g., a foot is planted on the floor) but the rest of the extremity remains in motion.
• Comminute Fracture: A fracture in which the bone has broken or fragmented into several pieces. It happens mostly due to crush.
• Impact Fracture: An impacted fracture is one whose ends are driven into each other.
• Green Sticks: fracture in a young, soft bone in which the bone bends and partially breaks

(ii) Open Fracture:

• Compound Fracture: An open fracture, also called a compound fracture, is an injury that occurs when there is a break in the skin around a broken bone. In order for an injury to be classified as a compound fracture, the outside air (and dirt and bacteria must be able to get to the fracture site without a barrier of skin or soft-tissue.

Answer 19.
Total number of teams =09
Upper half = n + 1/2 = 09+1/2 = 5
Lower half = n — 1/2 = 09-1/2 = 4
Power of two’s = 24 n. of teams
= 16-09 = 7
No.of Byes = 7
No.of Byes in Lower Half = nb+1/2 = 7+1=4
No. of Byes in Upper Half =  nb-1/2 = 7-1=3

Answer 20.
Role of sports in personality development are as following:
(i) Development of cognitive abilities: through sports participation cognitive process of athletes to perceive, evaluate and regulate their behaviour, which is appropriate in given situation improves. It benefits the following cognitive functions of processing information from received stimulus:

• Influence Intelligence
• Develops attention span
• Improves concentration

(ii) Control on arousal and emotion: sports participation helps in psycho-physiological activation helps in avoidance of negative emotions state of feeling of nervousness, apprehension associated with arousal of the body.

• Reduce anxiety
• Regulate aggression

(iii) Promote Social Cohesion: Sports participation

• Team association increases
• Task association increases

(iv) Create Leadership abilities: Sports participation helps in development of behaviour process of influencing individuals and groups towards set objectives. Athletes are able to take initiative and guide others in performing some required task in an organized form to task attainment. It help in the following:

• Develop ownership
• Creates responsibility

(v) Self-Efficacy: Sports participation develops belief in athletes to perform task successfully. Sports participation supports individual belief in his or her competencies and abilities to succeed in particular task.

Answer 21.
Role of nutrition in sports performance can be divided in three phases, Pre-competition, During Competition, Post Competition.
(i) Pre-Competition:

• Carbohydrate loading before competition helps in storing of glycogen which helps in extra energy during competitions.
• Sufficient intake of fluid before competitions help in prevention of dehydration.

(ii) During Competition:

• Small amount of carbohydrates at regular interval helps in maintain blood sugar level and reduces fatique.
• Frequent intake of fluids are beneficial to stay hydrated during high intensity level activities.

(iii) Post Competition:

• Initial intake of carbohydrate after competitions help in restoring glycogen.
• To enhance muscle recovery, protein diet after few hours of competition is helpful.
• A balanced diet containing of macro and micro nutrients post competitions helps in faster recovery and reduced chances of injury.

Essential nutrients required for performance:
Fat: it is major source of fuel, various sports require different proportion of fat to muscles, although extra fat influences performance.

Carbohydrates: it is a major fuel for muscular contraction. It helps in decrease of fatigue. Low level of carbohydrates results in formation of lactic acid leading to early fatigue. Protein: It is required for growth of tissues. Protein is used as for repair of cells and tissues leading to faster growth and development of muscles. It does have significant effect on performance.

Minerals: are essential for energy balance, deficiency decreases performance and increases chances of injury.

Vitamins: Essential for balance growth by avoiding deficiency. Vitamins protect the body from preventing external bodies to create damage and produce disease in the body.

Answer 22.
Protection, Rest, Ice, Compression and Elevation, or P.R.I.C.E., adds the concept of “protection” to the traditional R.I.C.E. protocol formula. Protecting the injured area from further damage is crucial to the healing process.
P: Protection is meant to prevent further injury. For example, an injured leg or foot may be protected by limiting or avoiding weight-bearing through the use of crutches, a cane, or hiking poles. Partially immobilizing the injured area by using a sling, splint, or brace may also be a means of protection.

R: Rest is important to allow for healing. However, many sports medicine specialists use the term “relative rest” meaning rest that allows for healing, but is not so restrictive that recovery is compromised or slowed. A person should avoid activities that stress the injured area to the point of pain or that may slow or prevent healing.

I: Ice refers to the use of cold treatments, also known as cryotherapy, to treat acute injuries.Ice is recommended with the intent to minimize and reduce swelling as well as to decrease pain. The most common and most convenient is a simple plastic bag of crushed ice placed over a paper towel on the affected area. It is important to protect the skin and limit the cold exposure to 10 to 15 minutes.
Skin sensitivity or allergy to cold exposure can occur. Skin may become mottled, red and raised where the ice contacted the skin. If this is experienced, the ice treatments should be discontinued.

C: Compression is the use of a compression wrap, such as an elastic bandage, to apply an external force to the injured tissue. This compression minimizes swelling and provides mild support.
Elastic bandage should be applied directly to the skin by starting a few inches below the injury and wrapping in a figure eight or spiraling manner to a few inches above the injured area.
A medium amount of tension should be applied to provide ample, but not too constrictive
compression. The bandage should not cause numbness, tingling, or color change of the soft ‘ tissue.
E: Elevation is recommended to help reduce the pooling of fluid in the injured extremity or joint. Controlling swelling can help decrease pain and may limit the loss of range of motion, possibly speeding up recovery time.

Answer 23.
Effect of exercise on cardiovascular system:
(i) Exercise Effect:

• Increase in stroke volume: it is the amount of blood ejected per beat from the left r ventricle. During activity SV increases 2-3 times from the resting SV.
• Increase in Heart Rate: Heart Rate is the amount of contraction of left ventricles per minute. During exercise HR increases.
• Cardiac Output: Cardiac Output is the amount of blood pumped from the heart per minute. Cardiac Output is the product of HR and S V. A resting Cardiac Output is 5L/ Min which can increase to 20 – 40 L/min after an intense exercise.
• Increase in Blood Flow: More amount of blood is required by the tissue for immediate demand. At rest, 15-20% of blood is released to skeletal muscles, whereas during intense exercise 80-85% of blood is transported to skeletal muscles.
• Increase in Blood Pressure: During exercise the systolic blood pressure increases 50¬70 mm/hg. Diastolic blood pressure remains unchanged.

(ii) Long Tem Effects:

• Increase in size of heart: Muscles of the heart increase in size. The left ventricle adapts
  to the greatest extent. This phenomenon is also called as ‘Cardiac Hypertrophy’ which is not a disease. –
• Decrease Resting Heart Rate: Regular exercise decreases the resting heart rate. Resting Heart Rate of 72beat/min can reduce to 30-40 beat/min in highly conditioned athletes.
• Increase in Resting Stroke Volume: After continuous training of several years, resting stroke volume increases to 70-0 ml/beat from 50-70 ml/beat.

Answer 24.
The parabolic path followed by a projectile is called its trajectory.
Factors:

1. Initial velocity: Initial velocity is directly related to the distance covered in flight. The speed of release depends on initial vertical velocity and initial horizontal velocity. Having higher horizontal velocity will increase the distance covered.
2. Angle of projection: An object which is projectedat different angles but the same initial velocity covers different distances. When it is released at an angle of 45o, covers maximum distance.
3. Projection height: The higher the level of release, the longer distance covered in the flight. The horizontal component will be acting on the projectile for longer duration; hence projectile will be covering a longer distance.
4. Gravity: Gravitational force is exerted by earth on all the objects. It is constant for all the objects. It decreases at the places of high altitude.
5. Spin: it is amount and direction of spin directly affects the distance covered. The spin covered low pressure on the top, the object remains in air for longer period covering longer distance. If the spin creates high pressure on the top, the object remains in air for shorter period and covers shorter distance.
6. Air Resistance: When a projectile moves through the air, it is slowed down by air resistance. It decreases the horizontal velocity of the projectile

Answer 25.
AAPHER motor fitness test was formed in 1965 in United States. It included these items:

• Pull ups (boys)
• Flexed arm stand (girls)
• sit ups 600 yard run walk
• shuttle run
• 50 yard dash etc.

1. Pull ups – to measure arm and shoulder strength
   Procedure – the bar was adjusted according to the height of the subject. The student is advised to raise his body so that the chin reaches the level of the bar. One score is awarded for each pull up. One trial is given.
2. Flexed arm stand – to measure arm and shoulder strength
   Procedure – the adjusted bar is held with hand grasp. The student lifts her body with the help of assistance of testing personnel so that has chin reaches the bar level. The clasped time is taken as score. The score is nearest second.
3. Sit ups – to measure abdominal strength and endurance
   Procedure – Student is advised to lie on floor on his/her back keeping knees bent. The angle of knees should be around 90°. Further the student is advised to put fingers interlockedand put behind the head. The student curls up and touches the elbows to knees. The score is counted as maximum number of sit ups in 60 seconds.
4. 50 yards Dash – to measure speed
   Procedure – the student is advised to run 50 yards and time is recorded nearest to 10th of a second.
5. 600 yard run walk – to measure endurance.
   Procedure – the student is advised to run or walk 600 yards and time is recorded in minutes and seconds.

Answer 26.
Regular physical activity helps elderly people to enjoy life and increases longevity along through wellbeing.

1. Immune Function: A healthy, strong body fights off infection and sickness more easily and more quickly. Rather than sapping energy reserves entirely, recovery from an illness will take less of a toll on the body if the person exercises regularly.
2. Cardio-Respiratory and Cardiovascular Function: Frequent physical activity lowers the risk of heart disease and high blood pressure. If the elderly person has hypertension, exercise will help lower their blood pressure.
3. Bone Density and Risk of Osteoporosis: Exercise protects against loss in bone mass. Better bone density will reduce the risk of osteoporosis, lower the risk of falling and prevent broken bones. Post-menopausal women can lose as much as 2 percent bone mass each year, and men also lose bone mass as they age. Research done at Tufts University shows that strength training can dramatically reduce this loss, help restore bones, and contribute to better balance and less fractures.
4. Gastrointestinal Function: Regular exercise helps boost your metabolism and promotes the efficient elimination of waste and encourages digestive health.
5. Chronic Conditions and Cancer: Physical activity lowers risk of serious conditions such as Alzheimer’s disease and dementia, diabetes, obesity, heart disease, osteoporosis and colon cancer, to name a few. It also helps in the management of high cholesterol and arthritis pain.
6. Manage Stress, Improve Mood: Regular, moderate physical activity can help manage stress and improve your mood. And, being active on a regular basis may help reduce feelings of depression. Studies also suggest that exercise can improve or maintain some aspects of cognitive function, such as your ability to shift quickly between tasks, plan an activity, and ignore irrelevant information.
7. Prevent or Delay Disease: Scientists have found that staying physically active and exercising regularly can help prevent or delay many diseases and disabilities. In some cases, exercise is an effective treatment for many chronic conditions. For example, studies show that people with arthritis, heart disease, or diabetes benefit from regular exercise. Exercise also helps people with high blood pressure, balance problems, or difficulty walking.

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CBSE Sample Papers for Class 12 Political Science Paper 1 for Class 12 Political Science Paper 1 are part of CBSE Sample Papers for Class 12 Political Science. Here we have given CBSE Sample Papers for Class 12 Political Science Paper 1.

CBSE Sample Papers for Class 12 Political Science Paper 1

Students who are going to appear for CBSE Class 12 Examinations are advised to practice the CBSE sample papers given here which is designed as per the latest Syllabus and marking scheme as prescribed by the CBSE is given here. Paper 1 of Solved CBSE Sample Paper for Class 12 Political Science is given below with free PDF download solutions.

Time Allowed: 3 hours
Maximum Marks: 80

General Instructions :

1. All questions are compulsory.
2. Questions nos. 1 to 5 are of 1 mark each. The answer to these questions should not exceed 20 words
3. Questions nos. 6 to 10 are of 2 marks each. The answer to these questions should not exceed 40 words
4. Questions nos. 11 to 16 are of 4 marks each. The answer to these questions should not exceed 100 words
5. Questions nos. 17 to 21 are of 5 marks each. The answer to these questions should not exceed 150 words
6. Questions no. 21 is map based question
7. Questions nos. 22 to 27 are of 6 marks each. The answer to these questions should not i exceed 150 words

Question 1.
Mention the period of First and Second World Wars.

Question 2.
Why is it said that the fall of Berlin Wall signified the end of bipolarity?

Question 3.
What is global poverty?

Question 4.
Why were the states reorganised on linguistic basis in India in 1956?

Question 5.
When and by whom was the Institutional Revolutionary Party (PRI) founded?

Question 6.
When and why did the New World Order begin?

Question 7.
Mention any two steps taken by China to improve its economy.

Question 8.
What is Indus River Water Treaty? Mention its significance also.

Question 9.
Who was J.C. Kumarappa?

Question 10.
What was Afro-Asian unity?

Question 11.
What was 9/11 event? How did the US respond to it?

Question 12.
In what ways does the present Chinese economy differ from its command economy?

Question 13.
India’s neighbours often think that the Indian government tries to dominate and interfere in the domestic affairs of the smaller
countries of the region. Is this a correct impression?

Question 14.
What was the task of the States Reorganisation Commission? What was its most salient recommendation?

Question 15.
In what sense was the Congress an ideological coalition ? Mention the various ideological currents present within the Congress.

Question 16.
What was the major thrust of the First Five Year Plan? In which ways did the Second Plan differ from the first one?

Question 17.
Read the passage given below carefully and answer the questions that follow:
The Western alliance was formalised into an organisation, the North Atlantic Treaty Organisation (NATO), which came into existence in April 1949. It was an association of twelve states which declared that armed attack on any one of them would be regarded as an attack on all of them. Each of these states would be obliged to help each other. The eastern alliance known as the Warsaw Pact was led by Soviet Union, created in 1955 and its principal function was to counter NATO’s forces in Europe.
(i) What does NATO stand for?
(ii) What was NATO’s policy?
(iii) What was Warsaw Pact?
(iv) Mention the main function of Warsaw Pact.

Question 18.
Read the following passage carefully and answer the questions:
In eastern Europe, Czechoslovakia split peacefully into two, with the Czechs and the Slovaks forming independent countries. But the most severe conflict took place in the Balkan republics of Yugoslavia. After 1991, it broke apart with several provinces like Croatia, Slovenia and Bosnia and Herzegovina declaring independence. Ethnic Serbs opposed this, and a massacre of non-Serb Bosnians followed. The NATO intervention and the bombing of Yugoslavia followed inter- ethnic civil war.
(a) In Eastern Europe which republic split into two?
(b) Name the republic/place where severe conflict took place.
(c) Name various provinces with which Yugoslavia had been broken in 1991.
(d) Which incidents resulted into inter-ethnic civil war?

Question 19.
Study the picture given below and answer the questions that follow:
(i) What message does the cartoon convey?
(ii) Name the person who is making efforts to balance both the sectors.
(iii) How was both these sectors balanced?

Question 20.
Read the passage carefully and answer the following questions:
ASEAN was and still remains principally an economic association. While the ASEAN region as a whole is a much smaller economy compared to the US the EU, and Japan, its economy is growing much faster than all these. This accounts for the growth in its influence both in the region and beyond. The objectives of the ASEAN Economic Community are to create a common market and production base within ASEAN States and to aid social and economic development in the region. The Economic Community would also like to improve the existing ASEAN Dispute Settlement Mechanism to resolve economic disputes. ASEAN has focused on creating a Free Trade Area (FTA) for investment, labour, and services. The US and China have already moved fast to negotiate FT As with ASEAN.
(i) What is the objective of ASEAN Economic Community?
(ii) Why did ASEAN establish Free Trade Areas (FTAs)?
(iii) How would ASEAN Economic Community resolve economic disputes?
(iv) Which countries have already moved fast to negotiate FTAs with ASEAN and why?

Question 21.
On a political outline map of the world, locate and label the following and symbolise them as indicated:

(i) The country that Iraq invaded in Aug. 1990.
(ii) The country under the Presidentship of Saddam Hussain.
(iii) The country referred to as a hegemonic power.
(iv) The Operation Infinite Reach was launched against these countries.

Question 22.
Examine the role played by India in the implementation of UN policies and programmes.
OR
Give a comparative analysis of Indian expenditure on traditional and non-traditional security.

Question 23.
What is meant by ‘Common but differentiated responsibilities’? How could we implement the idea?
OR
Critically evaluate the impact of the changing role of state in the developing countries in the light of globalisation ?

Question 24.
Describe the relationship of India with post-Communist countries.
OR
What are the constraints on American hegemony today? Which one of these do you expect to get more important in the future ?

Question 25.
Highlight the role of Pt. Nehru in
(i) Setting the national agenda.
(ii) Afro-Asian unity
OR
What were the factors which led to the popularity of Indira Gandhi’s Government in the ’ early 1970 s ?

Question 26.
The Shah Commission was appointed in 1977 by the Janata Party Government. Why was it appointed and what were its findings?
OR
What are popular movements? Explain any three issues related to women which brought social awareness amongst them.

Question 27.
What were the main provisions of the Punjab accord? In what way can they be the basis for further tensions between the Punjab and its neighboring States?
OR
Analyse India’s changing relationship with Russia post and communist countries.

Answers

Answer 1.
First World War: 1914-1918
Second World War: 1939-1945

Answer 2.
The collapse of Berlin Wall in 1989 is considered as the end of bipolarity as it was a symbol
of Cold War. Fall of Berlin Wall was followed by those events that led to the end of the Cold War.

Answer 3.
Global poverty signifies a condition available in the states to be suffered from low incomes and less economic growth i.e. developing or underdeveloped countries.

Answer 4.
States were reorganised on linguistic basis in India in 1956 to maintain unity and integrity of the nation to avoid violence and conflicts among the people.

Answer 5.
The Institutional Revolutionary Party (PRI) was founded in 1929 by Plutareo Elias Calles
in Mexico which represented the legacy of Mexican Revolution.

Answer 6.
The New World Order began in 1991 after the collapse of Soviet Union. The world was left
only with single superpower i.e. the US and came to be known as the US hegemony to show the superiority of its military power. The US hegemony also shaped world economy and emerged in the form of military domination, economic order, political clout and cultural superiority.

Answer 7.
(i) Special Economic Zones (SEZs) were created to invite foreign investors to set up their own enterprises.
(ii) The privatisation of agriculture and industry in 1982 and 1998.

Answer 8.
India and Pakistafi signed Indus River Water Treaty by the mediation of the World Bank in 1960 over the issue of sharing of rivers of the Indus basin. This treaty has been survived despite many military conflicts between these two countries.

Answer 9.
(i) J.C. Kumarappa was originally known as J.C. Cornelius. k
(ii) He was an economist and chartered accountant.
(iii) He was the follower of Mahatma Gandhi to apply Gandhian principles of economic policies.

Answer 10.
Bandung Conference was held in 1955 in Indonesia as an Afro-Asian conference to lead an establishment of NAM. It was held to mark the engagement of India with African and Asian nations known as Afro-Asian unity.

Answer 11.
9/11 event implies a series of attacks on the US by hijackers from Arab countries on 11
September 2001. It was the most disastrous attack on the US. The hijackers attacked on i important US building such as World Trade Centre in New York, Pentagon building and Capital building of US Congress in Pennsylvania.

The US responded to it by launching ‘Operation Enduring Freedom’ to arrest all those who were suspected to be behind this attack. The US forces made arrest all over the i world without the knowledge of the government of the persons being arrested, transported and detained them in secret prisons mainly against Al-Qaeda and Taliban regime in Afghanistan.

Answer 12.
The present Chinese economy has adopted the ‘open door policy’ to generate higher productivity by investments of capital and technology. It differed from its command economy in the following manner:
(i) It broke stagnancy of command economy.
(ii) Command economy lagged behind the industrial production but Chinese economy recovered it by privatisation of agriculture and industry.
(iii) The present Chinese economy established new trading laws and created Special Economic Zones leading higher rise in foreign trade. During Command economy the international trade was minimal and per capita income was very low.

Answer 13.
No, the impression is not correct because India makes efforts to manage its neighbours beyond its size and powers which can be justified on following grounds-
(i) India often feels exploited by its neighbours.
(ii) On the other hand, India’s neighbours fear that India wants to dominate them regionally but India is centrally located who shares borders with other countries geographically, which should be accepted on mutual understanding.
(iii) India avoids political instability in its neighbouring states so that outsiders shold not take advantage of influence in the region.

Answer 14.
The States Reorganisation Commission was set up in 1953 by Central Government to look into the matter of redrawing of boundaries of state:
(i) The Commission evolved that states’ boundaries should reflect the boundaries of different languages to accommodate linguistic diversity.
(ii) The States Reorganisation Act was passed in 1956 which resulted the creation of 14 states and 6 union territories.
(iii) Its most salient recommendation was the formation of linguistic states i.e. to reorganise states on the basis of accommodation of their languages to prepare a uniform base for the nation.

Answer 15.
The Congress Party became a social and ideological coalition for it merged different social groups along with their identity holding different beliefs:
(i) It accommodated the revolutionary, conservative, pacifist, radical, extremist and moderates and the rights and the left with all other shades of the centre.
(ii) The Congress became a platform for numerous groups, interests and even political parties to take part in the national movement.
Ideological currents present within the Congress:
(a) In pre-Independence days, many organisations and parties with their own Constitutions and organisational structures were allowed to exist within the Congress.
(b) Some of these like “Congress Socialist Party” later seperated from the Congress and became an opposition party.

Answer 16.
The First Five Year Plan was commenced in 1951 to be drafted by young economist K.N. Roy with the emphasis on poverty alleviation. Jawaharlal Nehru, the first Prime Minister of India presented this to the Parliament of India. Its main thrusts were as follows:

• To invest in dams and irrigation to improve agricultural sector with the urgent attention.
• Huge allocations were made for large scale projects like Bhakra-Nangal dam.
• It focused on land reforms for the development in rural areas.
• It aimed to increase level of national income.

The First Five Year plan differed from the Second Five Year plan:
(a) The Second Five Year Plan stressed on heavy industrialisation.
(b) It wanted to bring quick structural transformation in all possible directions in place of slow and steady growth like First Five Year Plan.

Answer 17.

• NATO stands for North Atlantic Treaty Organisation.
• NATO was an association of twelve states which declared that armed attack on any one of them would be regarded as an attack on all of them and each of them would be obliged to help each other.
• Warsaw Pact was eastern alliance led by Soviet Union, created in 1955.
• Main function of Warsaw Pact was to counter NATO’s forces in Europe.

Answer 18.
(a) Czechoslovakia split into two with Czechs and Slovaks.
(6) Balkan republics of Yugoslavia.
(c) Croatia, Slovenia, Bosnia and Herzegovina.
(d)
(i) Ethnic Serbs opposed the breaking up of several provinces independently following a massacre of non-serb Bosnians.
(ii) NATO intervention and bombing on Yugoslavia.

Answer 19.

1. Cartoon is trying to make balance between the private and public sectors to maintain the growth of an economy adopted by India.
2. Pt. Jawaharlal Nehru, the then Prime Minister of India.
3. Pt. Nehru made a*balance between both the sectors by adopting the model of mixed economy to co-exist the private and public sector.

Answer 20.

1. To create common market and production based activities within ASEAN states itself and to aid social and economic development.
2. Free Trade Areas have been established for investment, labour and services.
3. By improving the existing ASEAN Dispute Settlement Mechanism.
4. ASEAN is rapidly growing into areas of regional organisation with its Vision 2020.

Answer 21.

• Kuwait (A).
• Iraq (B).
• The USA (C).
• Afghanistan and Sudan (D) and (E).

Answer 22.

1. India believes that a strengthened and revitalised UN is desirable in the changing world.
2. India also supports an enhanced role for the UN in promoting development and cooperation among states.
3. India believes that the development should be central to the UN’s agenda as it is a vital precondition for the maintenance of international peace and security.
4. India debates more representation in Security Council may enjoy greater support in world community.
5. India has major concern about restructuring of UN Security Council.
6. India supports the role of developing countries should be represented in Security Council in decision making.

OR

India spends more on traditional security than non-traditional because

1. India has been involved in conflict with its neighbours as Pakistan in 1947-48, 1965, 1971 and 1999 and China in 1962.
2. In South Asian region, India is surrounded by nuclear armed countries. Hence, India’s decision to conduct nuclear test in 1990 was justified to safeguard national security.
3. India conducted its first nuclear detonation on 18 May 1974.

Though India has made efforts to develop its economy and an individual’s security from poverty but still it is lagging behind even now and we are supposed to make more efforts.

Answer 23.
Common but differentiated responsibilities mean that the state shall cooperate in the spirit of global partnership to conserve, protect and restore the health and integrity of the .earth’s ecosystem. As the states have common but differentiated responsibilities over various contributions of global environmental degradation. The developed countries acknowledge that the responsibility that they bear in the international pursuit of sustainable development in view of the pressures their societies place on the global environment and of the technological and financial resources they command.

We could implement the idea with the help of conventions and declarations:

1. The Rio-Summit held in June 1992 produced conventions dealing with climate change, biodiversity, forestry and recommended a list of developed practices called Agenda 21.
2. The 1992 United Nations Framework convention on climatic change (UNFCCC) also emphasised that the parties should act to protect the climate system on the basis of common but differentiated responsibilities.
3. An international agreement known as Kyoto Protocol set targets for industrialised countries to cut their greenhouse gas emissions which support for global warming.

OR

The impact of changing role of state in the developing countries in the light of globalisation can be summed up as follows:

1. Globalisation reduces the state capacity i.e. the ability of governments to do what they do.
2. Market becomes the prime concern to set down economic and social priorities.
3. Multinational companies effect on the decisions taken by government because their own interest fulfillment also depends on government policies.
4. The old welfare state is now giving way to more minimalist state to perform certain core functions as maintenance of law and order and the security.
5. State also withdraws from many of its welfare functions taken place at the level of
   economic and social well-being. .
6. To some extent developing countries have received a boost as a result of globalisation and became more strong and powerful clue to emergence of new technology.

Answer 24.
India has maintained good relations with all the post-communist countries, but the strongest relations are still those between Russia and India.

1. Indo-Russian relations are a significant aspect of India’s foreign policy. Their relations are embedded in history of trust and common interests and are matched by popular perceptions. For example, Indian heroes from Raj Kapoor to Amitabh Bachchan are household names in Russia and many post-Soviet countries.
2. Russia and India share a vision of multipolar world order i.e. co-existence of several world powers internationally, collective security, greater regionalism, democratisation with the decision-making through bodies like the UN.
3. More than 80 bilateral agreements have been experienced between India and Russia as a part of the Indo-Russia Strategic Agreement of 2001.
4. India has been benefitted from its relationship on the issues like Kashmir, energy supplies, sharing information on international terrorism, access to Central Asia and balanoing its relation with China.
5. Russia is also important for India’s nuclear energy plan and assisting India’s space industry by giving cryogenic rocket to India whenever needed.
6. Co-operation with Russia and its republics like Kazakhstan, Turkmenistan in the form of partnership and investment in oil fields has also benefitted India.
7. Russia is also “benefitted from India on ground of the second largest arms market.
   Indian military gets most of its hardware from Russia.
8. Russia and India have collaborated on various scientific projects also.

OR

“We can identify three constraints on American Power” which were actually not in operation in the years following 9/11. Hence, the US could establish its hegemony. Recently all these constraints are slowly beginning to operate in the following ways:

1. The US bears institutional architecture in the American State itself. It refers division of powers between the three branches of government where American military’s executive branch can place significant brakes upon the unrestrained and immoderate exercise.
2. The second constraint on American hegemony emerges from open nature of American society. American society and suffering from a deep skepticism towards purposes and methods of government in America despite an imposition of particular perspectives on domestic opinion in the US. This is a huge constraint on US military action overseas.
3. The third constraint on US hegemony is the possession of NATO to moderate the exercise of the US hegemony today. The US has an enormous interest in keeping the alliance of democracies to follow the market economies alive and it may be possible to its allies in NATO to moderate the exercise of the US hegemony through their own i liberal policies to fullfiel their own ends.

Answer 25.
1. Role of Pt. Nehru in setting the national agenda :
As the Prime Minister and Foreign Minister, Jawaharlal Nehru exercised profound influence in the formulation and implementation of India’s foreign policy from 1946 to 1964. The three major objectives of Nehru’s foreign policy were to preserve the . hard-earned sovereignty. Protect territorial integrity, and promote rapid economic development. Nehru wished to achieve these objectives through the strategy of non-alignment. There were, of course; Parties and groups in the country.
2. Role of Pt. Nehru in Afro-Asian unity :
Jawaharlal Nehru envisaged a crucial role for India in world affairs and in Asian _ affairs especially. His era was marked by the establishment of contacts between India and other newly independent states in Asia and Africa. Throughout the 1940s and 1950s, Nehru had been an ardent advocate of Asian unity. Under his leadership, India convened the Asian Relations Conference in march 1947, five months ahead of attaining its independence, and made earnest efforts for the early realisation of freedom of Indonesia from the Dutch colonial regime by convening an international conference in 1949 to support its freedom struggle.

OR

Because :

1. Socialist credentials became main projects during this period.
2. Indira Gandhi campaigned to implement land reform legislations and land ceiling legislations.
3. She ended her dependence on other political parties by strengthening her party’s position and recommended the dissolution of the LokSabha in December 1970.
4. The crisis in East Pakistan and Indo-Pak war to establish Bangladesh as an independent one, also enhanced the popularity of Indira Gandhi.
5. Indira Gandhi’s government was not accepted only as a protector of the poor and underprivileged but as a strong government also.
6. Congress became popular among different social sections and restored dominance again.

Answer 26.
The Shah Commission was appointed in May 1977 by Janata Party government which was headed by J.C. Shah, retired Chief Justice of the Supreme Court of India to look into the matters of:

• Allegations of abuse of authority
• Excesses and malpractices
• Actions taken in the name of emergency proclaimed on 25 June 1975.

The Commission performed to examine various evidences to give testimonies even including Indira Gandhi to appear before Commission, but she refused to answer any questions.
Findings of Shah Commission :
(a) It found many ‘excesses’ committed during Emergency.
(b) Under preventive detention laws nearly one lakh eleven thousand people were arrested.
(c) Press censorship took place without any proper legal sanctions.
(d) Even general manager of Delhi Power Supply Corporation received verbal orders from the officers of the Lt. Governor of Delhi to cut electricity to all newspapers press at 2 a.m. on 26 June 1975.

The Government of India accepted the findings, observation and recommendations contained the two interim reports and their and final report of the Shah Commission. The reports were also tabled in the two houses of Parliament.

OR

Popular movements are the movements organised by dalits and farmers under the banner of various social organisations to voice their demands.
Issues related to women which brought social awareness among them:

1. Chipko movement spread across many parts of Uttarakhand and larger issues of ecological and economic exploitation were also raised. Government issued a ban on felling of tress in Himalayan region for fifteen years until green cover was fully restored. Active participation of women was also a very novel aspect of the movement.
2. Anti-arrack movement was the movement of rural women in Andhra Pradesh to protest against alcoholism, mafias and government. This movement focused on issues of sexual violence against women either within family or outside. Women joined the campaign against dowry and demanded personal and property laws based on gender  equality. These campaigns contributed a great deal in increasing social awareness as well as shifted from legal reforms to open social confrontations.
3. Throughout seventies and eighties, local fish workers’ organisations fought with the State governments over the issues of their livelihood. Fisheries being a State subject, the fish workers were mostly mobilised at the regional level. With the coming of policies of economic liberalisation in and around the mid eighties, these organisations were compelled to come together on a national level platform-the National Fishworkers’ Forum (NFF). Fish workers from Kerala took the main responsibility of mobilising fellow workers, including women workers of other states.

Answer 27.
Punjab Accord was an agreement signed between the then Prime Minister Rajiv Gandhi and Harchand Singh Longowal, the then President of Akali Dal in 1985 to be known as ‘Rajiv Gandhi Longowal Accord’ also to create normalcy in Punjab:

• Chandigarh would be transferred to Punjab.
  
  Rajiv Gandhi and Harchand Singh Longowal, signatories of Punjab Accord of 1985
• To appoint a separate commission to resolve border dispute between Punjab and Haryana.
• To set up a tribunal to settle down the sharing of Ravi-Beas river water among Punjab, Haryana and Rajasthan.
• To provide agreement for compensation to better treatment to those affected by militancy in Punjab.
• To withdraw the Armed Forces Special Power Act in Punjab.

But, peace could not be established easily in Punjab and resulted as follows:
(a) It led to many excesses by police and violation of human rights.
(b) It fragmented the Akali Dal.
(c) The President’s rule was imposed and normal political process was suspended.
(d) Hence, political process could not be restored in this atmosphere. Even during elections in 1992, only 24% electors turned out to vote.

Consequently above mentioned added to tension between Punjab and its neighbouring states.

OR

India should not change its foreign policy and focus more on friendship with US, but India is required to maintain healthy relations with Russia because India has experienced a long band of mutual trust, interests and popular perceptions with Russia in the following
manner:

1. Russia and India share a vision of multipolar world order i.e. co-existence of several world powers internationally, collective security, greater regionalism, democratisation with the decision-making through bodies like the UN.
2. More than 80 bilateral agreements have been experienced between India and Russia as a part of the Indo-Russia Strategic Agreement of 2001.
3. India has been benefited from its relationship on the issues like Kashmir, energy supplies, sharing information on international terrorism, access to Central Asia and balancing its relation with China.
4. Russia is also important for India’s nuclear energy plan and assisting India’s space industry by giving cryogenic rocket to India whenever needed.
5. Co-operation with Russia and its republics like Kazakhstan, Turkmenistan in the form of partnership and investment in oil fields has also benefitted India.
6. Russia is also benefitted from India on ground of the second largest arms market for Russia. Indian military gets most of its hardware from Russia.
7. Russia and India have collaborated on various scientific projects also.

We hope the CBSE Sample Papers for Class 12 Political Science Paper 1 help you. If you have any query regarding CBSE Sample Papers for Class 12 Political Science Paper 1, drop a comment below and we will get back to you at the earliest.

These Sample papers are part of CBSE Sample Papers for Class 12 Biology. Here we have given CBSE Sample Papers for Class 12 Biology Paper 7.

CBSE Sample Papers for Class 12 Biology Paper 7

Students who are going to appear for CBSE Class 12 Examinations are advised to practice the CBSE sample papers given here which is designed as per the latest Syllabus and marking scheme as prescribed by the CBSE is given here. Paper 7 of Solved CBSE Sample Paper for Class 12 Biology is given below with free PDF download solutions.

Time Allowed: 3 hours
Maximum Marks: 80

General Instructions:

1. There are total 26 questions and five sections in the question paper. All questions are compulsory.
2. Section A contains question number 1 to 5, Very Short Answer Type Questions of one mark each.
3. Section B contains question number 6 to 10, Short Answer Type Questions of two marks each.
4. Section C contains question number 11 to 22, Short Answer Type Questions of three marks each.
5. Section D contains question number 23, Value Based Question of four mark.
6. Section E contains question number 24 to 26, Long Answer Type Questions of five marks each.
7. There is no overall choice in the question paper, however, an internal choice is provided in one question of two marks, one question of three marks and all three questions of five marks. An examiner is to attempt any one of the question out of the two given in the question paper with the same question number.
8. No. of printed pages are three.

SECTION-A

Question 1.
A human zygote has XXY sex chromosomes along with 22 pairs of autosomes. What sex will the individual be?

Question 2.
Define linkage.

Question 3.
What is Brood Parasitism?

Question 4.
Which enzyme is known as ‘molecular scissors’?

Question 5.
Expand ELISA.

 SECTION-B

Question 6.
Give an account of surgical sterilization methods in males and females.

Question 7.
What are biological response modifiers?

Question 8.
What are histones?

Question 9.
What is soluble RNA? Illustrate.

Question 10.
What are the pre-fertilisation events in plants?

SECTION-C

Question 11.
Write the importance of bagging of unisexual flowers in crop improvement programme.

Question 12.
Elaborate the asexual mode of reproduction in the following:
(a) Chalmydomonas
(b) Hydra
(c) Yeast

Question 13.
What are the symptoms of the disease which are confirmed by a Widal test?

OR

What are the complexities involved in transcription of eukaryotic DNA?

Question 14.
Describe the responsibility of GEAC, set up by the Indian Government.

Question 15.
Explain the hormonal control of spermatogenesis in humans.

Question 16.
During his studies on genes in Drosophila that were sex-linked, T.H. Morgan found population
phenotypic ratios deviated from expected 9 : 3 : 3 : 1. Explain the conclusion he arrived at. 3

Question 17.
A person claimed that he has seen sounds, heard colours and smelt light.
(1) What could be the possible reasons?
(2) Name two chemicals responsible for this condition.
(3) Mention any one source of these chemicals.

Question 18.
What are the requisites of a cloning vector?

Question 19.
Explain gene therapy with an example.

Question 20.
What are the factors that contribute to Population density?

Question 21.
(a) Name the technology that has helped the scientists to propagate on large scale the desired crops in short duration. List the steps carried out to propagate the crops by the said technique.
(b) How are the somatic hybrid obtained?

Question 22.
What is “The Evil Quartet?

SECTION-D

Question 23.
Hanshal purchased one high milk yielding exotic breed of cow. Within a few years he earned lot of money by selling calves by using MOET. The mother cow met with a premature death. Raman objected to Hansal earning money by this way.
(a) What values in life did Raman possess?
(b) Expand MOET.
(c) Briefly describe the process.

SECTION-E

Question 24.

The following graph shows the species-area relationship. Answer the following questions as directed: 5
(a) Name the naturalist who studied the kind of relationship shown in the graph. Write observations made by him.
(b) Write the situations as discovered by the ecologists when the value of ‘Z’ (slope of the line) lies between
1. 0.1 and 0.2
2. 0.6 and 1.2
What does ‘Z’ stand for?
(c) When would the slope of the line ‘ff become steeper?

OR

List the observations of Human Genome Project

Question 25.
Explain and illustrate the development of the embryo sac.

OR

How are infertility problems overcome?

Question 26.
Elaborate on the key abiotic elements that contribute to the variation in habitats.

OR

Explain sickle cell anemia and its inheritance as a pedigree chart.

Answers

SECTION-A

Answer 1.
The individual will be a male.

Answer 2.
When two genes in a dihybrid cross are situated on the same chromosome, the proportion of
parental gene combinations is much higher than the non-parental type. This physical association of genes on a chromosome is termed as linkage.

Answer 3.
The parasitic bird lays it eggs in the nest of its host and lets the host bird incubate its eggs.
This is called Brood parasitism. The eggs of the parasitic bird have evolved to resemble the host’s egg in size and colour to reduce the chances of the host bird detecting the foreign eggs and ejecting them from the nest.

Answer 4.
Restriction enzymes.

Answer 5.
Enzyme Linked Immuno Sorbent Assay.

SECTION-B

Answer 6.
Surgical Sterilization method in male is called ‘vasectomy’ where a small part of the vas deferens is removed or tied up through a small incision on the scrotum.
The surgical method followed in female is called tubectomy where a small part of the fallopian tube is removed or tied up through a small incision in the abdomen or through vagina.

Answer 7.
Biological Response Modifiers (BRM) are the substances given to the cancer patients which activates the immune system for detection and destroying of tumor cell. For example, interferon. List the specific symptoms of typhoid. Name its causative agent.

Answer 8.
Specific symptoms of typhoid are:

1. Constant high fever (39° to 40° C).
2. Weakness
3. Stomach pain
4. Loss of appetite.

Its causative agent is Salmonella typhi.

OR

Histones are positively charged, basic proteins that are organised to form a unit of eight molecules called as histones octamer. The negatively charged DNA is wrapped around the positively charged histone octamer to form a structure called nucleosome.

Answer 9.
Soluble RNA or tRNA is an adapter molecule that would on one hand read the code and on other hand bind to the specific amino acids thereby facilitating protein synthesis. The term was coined by Francis Crick.

Answer 10.
The two main pre-fertilisation events in plants are:
(1) Gametogenesis: Refers to the process of formation of two gametes — male and female.
These gametes can be homogametes (haloid) or heterogametes (diploid), sperm and ovum.
(2) Gamete Transfer: Male and female gametes are physically brought together to facilitate fusion.

SECTION-C

Answer 11.
Bagging is a process where the emasculated flowers are covered with a bag of butter paper to prevent contamination of stigma with unwanted pollen. When this stigma attains receptivity, mature pollen grains of the desired plants with required traits are dusted on the stigma and the flowers are rebagged to allow the fruits to develop. This ensures the pollen grains of only desired plants are used for fertilisation of the stigma to develop the desired plant variety.

Answer 12.
Chlamydomonas is an alga which reproduces by formation of zoospores which are
(a) micropscopic motile structures.

(b) Hydra reproduces by the formation of buds which bud from the parent body.

(c) In Yeast, the division is unequal and small buds are produced that remain attached initially to the parent cell which, eventually gets separated and mature into new yeast organisms.

Answer 13.
Typhoid fever is confirmed by Widal test.
Substained high fever (39° to 40°C), weakness, stomach pain, constipation, headache and loss of appetite are some of the common symptoms of this disease. Intestinal perforation and death may occur in severe cases.

OR

There are two complexities involved in transcription of eukaryotic DNA:
(a) There are at least three RNA polymerases in the nucleus (in addition to the RNA polymerase found in the organelles)

• The RNA polymerase I transcribes rRNAs (28S, 18S, and 5.85), whereas the
• The RNA polymerase II transcribes precursor of mRNA, the heterogeneous nuclear RNA (hnRNA).
• RNA polymerase III is responsible for transcription of tRNA, and 5snRNA, and snRNAs
  (small nuclear RNAs)

(b) Secondly, the primary transcripts contain both the exons and the introns which are non-functional. Hence, it is subjected to a process called splicing where the introns are removed | and exons are joined in a defined order.

Answer 14.
GEAC (Genetic Engineering Approval Committee) is an Indian Government organisation. Its  responsibilities are:
(1) To examine the validity of GM (Genetic Modification of Organism) research.
(2) To inspect the safety of introducing GM for public services and for their large scale use.

Answer 15.
Spermatogenesis starts at the age of puberty due to significant increase in the secretion of
Gonadotropin Releasing Hormone (GnRH). The increased levels of GnRH then acts at
the anterior pituitary gland and stimulates secretion of two gonadotropins – Luteinising
[ Hormone (LH) and Follicle Stimulating Hormone (FSH). LH acts at the Leydig cells and
stimulates synthesis and secretion of androgens. Androgens, in turn, stimulate the process of spermatogenesis. FSH acts on the sertolli cells and stimulates secretion of some factors which
f help in the process of spermiogenesis.

Answer 16.
He observed that when the two genes in a dihybrid cross are located on the same chromosome the proportion of parental gene combinations in the progency was much higher than the non-parental or recombination of genes:
(1) Morgan and his group found that when genes are grouped on the same chromosome, some genes are tightly linked and show less recombination.
(2) When the genes are loosely linked, they show higher combination.

Answer 17.
(1) Hallucination.
(2) LSD, Cocaine.
(3) Erythroxylum cocal/Athropa belladona/Datura sps.

Answer 18.
Requisites of a cloning vector are:
(a) Origin of replication (ori): This is a sequence where replication of DNA starts within the host cells.

(b) Selectable Marker: These help in identifying and eliminating non-transformants and selectively permits the growth of the transformants.

(c) Cloning sites: This involves linkage of the alien DNA of the vector to a recognition sites
for the commonly used restriction enzymes.

Answer 19.
Gene therapy is a technique of genetic engineering with a collection of methods that allows correction of a gene defect that has been diagnosed in child/embryo by the insertion of a normal functional gene into the individual or embryo to take over the function of and compensate for the non-functional gene.
For example, the first clinical gene therapy was given for adenosine deaminase (ADA) deficiency which was caused due to the deletion of the gene for adenosine deaminase. It can be cured by bone marrow transplantation or enzyme replacement therapy, in which functional ADA is given to the patient by injection.
Steps included in Gene therapy are:

1. Lymphocytes from the blood of the patient are grown in a culture outside the body.
2. A functional ADA cDNA (using a retroviral vector) is then introduced into these lymphocytes, which are subsequently returned to the patient.
3. Periodic infusion of such genetically engineered lymphocytes into the patient.
4. The gene isolated from marrow cells producing ADA introduced into cells at early embryonic stages could be a permanent cure.

Answer 20.
The density of a population in a given habitat during a given period, fluctuates due to changes in four basic processes.
(a) Natality refers to the number of births during a given period in the population that are added to the initial density.
(b) Immigration is the number of individuals of the same species that have come into the habitat from elsewhere during the time period under consideration.
(c) Mortality is the number of deaths in the population during a given period.
(d) Emigration is the number of individuals of the population who left the habitat and gone elsewhere during the time period under consideration.
Hence, Natality and Immigration contribute to an increase in population density whereas Mortality and Emigration decrease it.

Answer 21.
(a) The technology that has helped the scientists to propagate the desired crops on large scale is tissue culture or micropropagation.
The steps to propagate crops are:

1. Obtaining an explant from a plant.
2. Growing the explant in a test tube under sterile conditions.
3. A special nutrient or culture medium is provided for growth.

(b) Isolated single cells are separated from the plants. Their cell walls are digested to obtain protoplasts. Isolated protoplasts from two different plant varieties are fused to get hybrid protoplasts.

Answer 22.
Accelerated rates of species extinction are due to four main causes which is called the Evil Quartet. These are:
(a) Habitat loss and fragmentation
(b) Over-exploitation
(c) Alien species invasions
(d) Co-extinctions.

SECTION-D

Answer 23.
(a) Raman was bold, having love for animals. He had ethics and prudence.
(b) Multiple Ovulation Embryo Transfer Technology.
(c) A cow is administered with FSH-like activity, to induce follicular maturation and super ovulation to produce 6-8 eggs in a single cycle.

1. The superovulated cow is either mated with an elite bull or artificially inseminated,
2. The fertilised eggs at 8-32 cells stages, are recovered non-surgically and transferred to surrogate mothers.
3. The genetic mother is available for another round of super ovulation.

SECTION-E

Answer 24.
(a) Alexander Von Humboldt
He observed that within a region, species richness increased in explored area but only up to a limit.
(b)

1. The slopes regression lines are similar when unaffected distribution in an area is analysed.
2. The slope of regression is steeper when we analyse the species area relationship among very large areas like entire continent. Z (slope of line) is the regression co-efficient.

(c) If species richness is more, i.e., in the range 0.62-1.2.

OR

The salient observations drawn from Human Genome Project are:

1. The human genome contains 3164.7 million nucleotide bases.
2. The average gene consists of 3000 bases, but sizes very greatly, with the largest known human gene being dystrophin at 2.4 million bases.
3. The total number of genes is estimated at 30,000-much lower than previous estimates of 80,000 to 1,40,000 genes. Almost all (99.9 per cent) nucleotide bases are exactly the same in all people.
4. The functions are unknown for over 50 per cent of the discovered genes.
5. Less than 2 per cent of the genome codes for proteins.
6. Repeated sequences make up very large portion of the human genome.
7. Repetitive sequences are stretches of DNA sequences that are repeated many times, sometimes hundred to thousand times. They are thought to have no direct coding functions, but they shed light on chromosome structure, dynamics and evolution.
8. Chromosome 1 has most genes (2968), and the Y has the fewest (231).
9. Scientists have identified about 1.4 million locations where singlebase DNA differences (SNPs-single nucleotide polymorphism, pronounced as ‘snips’) occur in humans. This information/promises to revolutionise the processes of finding chromosomal locations for disease-associated sequences and tracing human history.

Answer 25.
The nucleus of the functional megaspore divides mitotically to form two nuclei which move to the opposite poles, forming the 2-nucleate embryo sac. Two more sequential mitotic nuclear divisions result in the formation of the 4-nucleate and later the 8-nucleate stages of the embryo sac. Nuclear divison are not followed immediately by cell wall formation. After the 8-nucleate stage, cell walls are laid down leading to the organisation of the typical female gametophyte or embryo sac. Six of the eight nuclei are surrounded by cell walls and organised into cells; the remaining two nuclei, called polar nuclei are situated below the egg apparatus in the large central cell. There is a characteristic distribution of the cells within the embryo sac. Three

cells are grouped together at the micropylar end and constitute the egg apparatus. The egg apparatus, in turn, consists of two synergids and one egg cell. The synergids have special celluclar thickenings at the micropylar tip called filiform apparatus, which play an important role in guiding the pollen tubes into the synergid. Three cells are at the chalazal end and are called the antipodals. The large central cell has two polar nuclei. Thus, a typical angiosperm embryo sac, at maturity is 8-nucleate and 7-celled.

OR

Infertility problems are overcome by Assisted Reproductive Technologies (ART). Some ART techniques are depicted below:
(a) In vitro fertilisation (IVF): This method is popularly known as test tube baby programme, where ova from the wife/donor (female) and sperms from the husband/donor (male) are collected and are induced to form zygote under simulated conditions as that in the body followed by embryo transfer (ET) in the laboratory.
The zygote or early embryo with upto 8 blastomeres is then transferred into the fallopian tube (ZIFT-zygote infra fallopian transfer). If the embryo is with more than 8 blastomeres, it is transferred into the uterus (IUT-intra uterine transfer) to complete its further development. This technique can also be used to assist females who cannot conceive.

(b) GIFT-Gamete Intro Fallopian Transfer: Here, ovum collected from a donor is transferred into the fallopian tube of another female who cannot produce one but can provide suitable environment for fertilisation.

(c) Intra Cytoplasmic Sperm Injection (ICSI): An embryo in the laboratory is formed by injecting sperm directly into the ovum. The embryo so formed is later transferred by IUT. (e) Artificial Insemination (AI) Technique: In this technique, the semen collected either from the husband or a healthy donor is artificially introduced either into the vagina or into the uterus (IUI-intra-uterine insemination) of the female.

Answer 26.
The important abiotic components that contribute to the variation in habitats are:
(1) Temperature: It affects the kinetics of enzymes activity and other physiological functions of the organism. The levels of thermal tolerance of different species also determine their geographical distribution to a larger extent.

(2) Water: The productivity and distribution of plants is heavily dependent on water. For aquatic organisms the quality (chemical composition, pH and salinity) of water becomes important. Some organisms are tolerant of a wide range of salinities while others are restricted to a narrow range (stenohaline). Many freshwater animals cannot live for long in sea water and vice versa because of the osmotic problems, they would face.

(3) Light: It is required for
(a) photosynthesis,
(b) flowering, and
(c) diurnal and seasonal migrations of organisms, for e.g., photopheriodism and hibernation.

(4) Soil: It is a very important ecological factor as it provides water, minerals and nutrients and support to the producers.

OR

Sickle cell anemia is an autosome linked recessive trait that can be transmitted from parents to the offspring when both the partners are carrier for the gene (or heterozygous).
The disease is controlled by a single pair of allele, HbA and HbS. Out of the three possible genotypes only homozygous individuals for HbS (HbSHbS) show the diseased phenotype. Heterozygous (HbAHbS) individuals appear apparently unaffected but they are carrier of the diseases as there is 50 per cent probability of transmission of the mutant gene to the progeny, thus exhibiting sickle-cell trait. The defect is caused by the substitution of Glutamic acid (Glu) by Valine (Val) at the sixth position of the beta globin chain of the haemoglobin molecule. The substitution of amino acid in the globin protein results due to the single base substitution at the sixth codon of the beta globin gene from CAG to GUG. The mutant haemoglobin molecule undergoes polymerisation under low oxygen tension causing the change in the shape of RBC from biconcave disc to elongated sickle like structure.

We hope the CBSE Sample Papers for Class 12 Biology Paper 7 help you. If you have any query regarding CBSE Sample Papers for Class 12 Biology Paper 7, drop a comment below and we will get back to you at the earliest.

CBSE Sample Papers for Class 12 Physics Paper 6 are part of CBSE Sample Papers for Class 12 Physics. Here we have given CBSE Sample Papers for Class 12 Physics Paper 6.

CBSE Sample Papers for Class 12 Physics Paper 6

Time Allowed : 3 Hours

Max. Marks : 70

General Instructions 

• All questions are compulsory. There are 26 questions in all.
• This question paper has five sections: Section A, Section B, Section C, Section D and Section E.
• Section A contains five questions of 1 mark each. Section B contains five questions of 2 marks each. Section C contains twelve questions of 3 marks each. Section D contains one value based question of 4 marks and Section E contains three questions of 5 marks each.
• There is no overall choice. However, an internal choice has been provided in 1 question of 2 marks, 1 question of 3 marks and all the 3 questions of 5 marks weightage. You have to attempt only 1 of the choices in such questions.
• You may use the following values of physical constants wherever necessary :

Questions
SECTION : A

Question 1.
What are permanent magnets? Give one example.

Question 2.
What is the geometrical shape of equipotential surface due to a single isolated charge?

Question 3.
Which of the following waves can be polarized
(i) Heat waves
(ii) Sound waves? Give reason to support your answer.

Question 4.
A capacitor has been charged by a dc source. What are the magnitude of conduction and displacement current, when it is fully charged?

Question 5.
Write the relationship between angle of incidence ‘i’, angle of prism ‘A’ and angle of minimum deviations A_m for a triangular prism.

SECTION : B

Question 6.
The given graph shows the variation of photo-electric current (I) versus applied voltage (V) for two different photosensitive materials and for two different intensities of the incident radiations. Identify the pairs of curves that correspond to different materials but same intensity of incident radiation.

Question 7.
A 10 V battery of negligible internal resistance is connected across a 200 V battery and a resistance of 38 Ω as shown in the figure. Find the value of the current in circuit.

Question 8.
The emf of a cell is always greater than its terminal voltage. Why? Give reason.

Question 9.
(a) Write the necessary conditions for the phenomenon of total internal reflection to occur.
(b) Write the relation between the refractive index and critical angle for a given pair of optical media.

Question 10.
State Lenz’s law. A metallic rod held horizontally along east-west direction, is allowed to fall under gravity. Will there be an emf induced at its ends? Justify your answer.

SECTION : C

Question 11.
A convex lens of focal length 25 cm is placed co-axially in contact with a concave lens of focal length 20 cm. Determine the power of the combination. Will the system be converging or diverging in nature?

Question 12.
An ammeter of resistance 0.80 Ω can measure current up to 1.0 A.
(i) What must be the value of shunt resistance to enable the ammeter to measure current up to 5.0 A?
(ii) What is the combined resistance of the ammeter and the shunt?

Question 13.
In the given circuit diagram a voltmeter ‘V is connected across a lamp ‘L’. How would
(i) the brightness of the lamp and
(ii) voltmeter reading ‘V’ be affected, if the value of resistance ‘R’ is decreased? Justify your answer.

Question 14.
(a) An EM wave is travelling in a medium with a velocity v = v\(\overrightarrow { i }\) . Draw a sketch showing the propagation of the EM wave, indicating the direction of the oscillating electric and magnetic fields.
(b) How are the magnitudes of the electric and magnetic fields related to velocity of the EM wave?

Question 15.
Block diagram of a receiver is shown in the figure :
(a) Identify ‘X’ and ‘Y’
(b) Write their functions.

Question 16.
Explain, with the help of a circuit diagram, the working of a photo diode. Write briefly how it is used to detect the optical signals.

OR

Mention the important consideration required while fabricating a pn-j unction diode to be used as a Light Emitting Diode (LED). What should be the order of band gap of an LED if it is required to emit light in the visible range?

Question 17.
(a) Why photoelectric effect cannot be explained on the basis of wave nature of light? Give reasons.
(b) Write the basic features of photon picture of electromagnetic radiation on which Einstein’s photoelectric equation is based.

Question 18.
A capacitor of unknown capacitance is connected across a battery of V volts. The charge stored in it is 360 μC. When potential across the capacitor is reduced by 120 V, the charge stored in it becomes 120 μC.
Calculate :
(i) The potential V and the unknown capacitance C.
(ii) What will be the charge stored in the capacitor, if the voltage applied had increased by 120 V?

OR

A hollow cylindrical box of length 1 m and area of cross section 25 cm is placed in a three dimensional coordinate system as shown in the figure. The electric field in the region is given by \(\overrightarrow { E }\) = 5Ox \(\overrightarrow { i }\) where E is in NC andx is in metres.

Find
(i) Net flux through the cylinder.
(ii) Charge enclosed by the cylinder.

Question 19.
(a) In a typical nuclear reaction, e.g.

although number of nucleons is conserved, yet energy is released. How? Explain.
(b) Show that nuclear density in a given nucleus is independent of mass number A.

Question 20.
Write three important factors which justify the need of modulating a message signal. Show diagrammatically how an amplitude modulated wave is obtained when a modulating signal is superimposed on a carrier wave.

Question 21.
A metallic rod of length L is rotated with a frequency v with one end hinged at the centre and the other end at the circumference of a circular metallic ring of radius r, about an axis passing through the centre and perpendicular to the plane of the ring. A constant uniform magnetic field B parallel to the axis is present everywhere. Using Lorentz force, explain how emf is induced between the centre and the metallic ring and hence obtained the expression for it.

Question 22.
Output characteristics of an n-p-n transistor in CE configuration is shown in the figure.
Determine :
(i) dynamic output resistance
(ii) dc current gain and
(iii) ac current gain at an operating point V_CE = 10 V, when I_B = 30 pA.

SECTION : D

Question 23.
While travelling back to his residence in the car, Mr. Ram was caught up in a thunderstorm. He stopped driving the car and waited for thunderstorm to stop. He saw a child standing under the tree. He asked the boy not to stand under a tree in thunderstorm and to come inside the car till the thunderstorm stopped. Later he dropped the boy at his residence. The boy requested that he should meet his parents. The parents expressed their gratitude to him for his concern for safety of their child.
Answer the following questions based on the above information :

1. Why is it safer to sit inside a car during a thunderstorm?
2. Which two values are displayed by Mr. Ram in his action?
3. Which values are reflected in parents’ response to Mr. Ram?
4. Give an example of similar action on your part from everyday life.

SECTION : E

Question 24.
(a) Draw a ray diagram showing the image formation by a compound microscope. Hence obtain expression for total magnification when the image is formed at infinity.

OR

(a) State Huygens principle. Using this principle draw a diagram to show how a plane wave front incident at the interface of the two media gets refracted when it propagates from a rarer to a denser medium. Hence verify Snell’s law of refraction.
(b) When monochromatic light travels from a rarer to a denser medium, explain the following, giving reasons:
(i) Is the frequency of reflected and refracted light same as the frequency of incident light?
(ii) Does the decrease in speed imply a reduction in the energy carried by light wave?

Question 25.
(a) State the working principle of a potentiometer. With the help of the circuit diagram, explain how a potentiometer is used to compare the emfs of two primary cells.  Obtain the required expression used for comparing the emfs.
(b) Write two possible causes for one sided deflection in a potentiometer experiment.

OR

(a) State Kirchhoff’s rules for an electric network. Using Kirchhoff’s rules, obtain the balance condition in terms of the resistance of four arms of Wheatstone bridge.
(b) In the meter bridge experimental set up, shown in the figure, the null point ‘D’ is obtained at a distance of 40 cm from end A of the meter bridge wire. If a resistance of 10 Q is connected in series with R₁, null point is obtained at AD = 60 cm. Calculate the values of R₁ and R₂

Question 26.
(a) Derive the expression for the torque on a rectangular current carrying loop suspended in a uniform magnetic field.
(b) A proton and a deuteron having equal momenta enter in a region of a uniform magnetic field at right angle to the direction of the field. Depict their trajectories in the field.

OR

(a) A small compass needle of magnetic moment ‘m’ is free to tum about an axis perpendicular to the direction of uniform magnetic field ‘B’. The moment of inertia of the needle about the axis is T. The needle is slightly disturbed from its stable position and then released. Prove that it executes simple harmonic motion. Hence deduce the expression for its time period.
(b) A compass needle, free to turn in a vertical plane orients itself with its axis vertical at a certain place on the earth. Find out the values of
(i) horizontal component of earth’s magnetic field and
(ii) angle of dip at the place.

Answers
SECTION : A

Answer 1.
The magnets which have high retentivity and high coercivity are known as permanent magnets. For example : Steel.

Answer 2.
The equipotential surfaces of an isolated charge are concentric spherical shells and the distance between the shells increase with the decrease in electric field and vice-versa.

Answer 3.
Heat waves can be polarized as they are transverse waves whereas sound waves cannot be polarized as they are longitudinal waves. Transverse waves can oscillate in the direction perpendicular to the direction of its transmission but longitudinal waves oscillate only along the direction of its transmission. So, longitudinal waves cannot be polarized.

Answer 4.
Electric flux through plates of capacitor,

Here q is constant, the capacitor is fully charged.

As voltage becomes constant when capacitor is fully charged.

Answer 5.
The relation between the angle of incidence i, angle of prism A, and the angle of minimum deviation A , for a triangular prism is given by i = (A + A_m)/2

SECTION : B

Answer 6.
Curves 1 and 2 correspond to similar materials while curves 3 and 4 represent different materials, since the value of stopping potential for 1,2 and 3,4 are the same. For the given frequency of the incident radiation, the stopping potential is independent of its intensity.

So, the pairs of curves ( 1 and 3) and (2 and 4) correspond to different materials but same intensity of incident radiation.

Answer 7.

Since, the positive terminal of the batteries are connected together, so the equivalent emf of the batteries is given by
E = 200- 10= 190 V
Hence, the current in the circuit is given by
I = E/R = 190/38 = 5 A

Answer 8.
The emf of a cell is greater than its terminal voltage because there is some potential drop across the cell due to its small internal resistance.

Answer 9.
(a) Necessary conditions for total internal reflection to occur are :

1. The incident ray on the interface should travel in optically denser medium.
2. The angle of incidence should be greater than the critical angle for the given pair of optical media.

(b)

Where a and b are the rarer and denser media respectively. C is the critical angle for the given pair of optical media.

Answer 10.
Lenz’s law states that the polarity of induced emf is such that it produces a current which opposes the change in magnetic flux that produces it. Emf will be induced in the rod as there is change in magnetic flux.

When a metallic rod held horizontally along east-west direction, is allowed to fall freely under gravity i.e. fall from north to south, the magnetic flux changes and the emf is induced in it.

SECTION : C

Answer 11.
We have focal length of convex lens,
f₁  = +25 cm = +0.25 m
Focal length of the concave lens,
f₁ = -20 cm = -0.20 m
Equivalent focal length,

∴ The focal length of the combination = -1 m = -100 cm As the focal length is negative, the system will be diverging in nature.

Answer 12.
We have, resistance of ammeter, R_A = 0.80 ohm
Maximum current across ammeter, I_A = 1.0 A.
So, voltage across ammeter, V= IR = 1 x 0.80 = 0.8 V
Let the value of shunt be x.
(i) Resistance of ammeter with shunt,

(ii) Combined resistance of the ammer and the shunt,

Answer 13.

The given figure is Common Emitter (CE) configuration of an n-p-n transistor. The input circuit is forward biased and collector circuit is reverse biased. If resistance R decreases, forward biased in the input circuit will increase, thus the base current (I_B) will decrease and the emitter current (I_E) will increase. This will increase the collector current (I_c) as
(I_E) = (I_B) + (I_c).
When I_c increases which flows through the lamp, the voltage across the bulb will also increase making the lamp brighter and the voltmeter is connected in parallel with the lamp, the reading in the voltmeter will also increase.

Answer 14.
(a) Given,
Velocity, v = v \(\overrightarrow { i }\) and E is the electric field along Y-axis and B is the magnetic field along Z-axis.
The propagation of EM wave is shown below :

(b) Speed of EM wave can be given as the ratio of magnitude of electric field (E₀) to the magnitude of magnetic field (B₀)

Answer 15.
From the given block diagram of demodulator of a typical receiver, we can conclude the following things :
(a) X represents Intermediate Frequency (IF) stage while Y , represents an amplifier.
(b) At IF stage, the carrier frequency is transformed to a lower frequency then in this process, the modulated signal is detected. The function of amplifier is to amplify the detected signal which may not be strong enough to be made use of and hence is essential.

Answer 16.
A junction diode made from light sensitive semiconductor is called a photo diode.

An electrical device that is used to detect and convert light into an energy signal with the use of a photo detector is known as a photo diode. The light that falls on it controls the function of pn-junction. Suppose, the wavelength is such that the energy of a photon hcfk is enough to break a valence bond. There is an increase in number of charge carriers and hence the conductivity of the junction also increases. New hole-electron pairs are created when such light falls on the junction. If the junction is connected in a circuit, the intensity of the incident light controls the current in the circuit.

OR

1. The reverse breakdown voltage of LEDs are very low, which is around 5 V. So enough care is to be taken while fabricating a pn-junction diode such that the high reverse voltages do not occur across them.
2. There exist very small resistance to limit the current in LED. So, a resistor must be placed in series with the LED such that no damage is occurred to the LED.The semiconductor used for fabrication of visible LEDs must atleast have a band gap of 1.8 eV.

Answer 17.
(a) Wave nature of radiation cannot explain the photoelectric effect because of :

1. The immediate ejection of photo electrons.
2. The presence of threshold frequency for a metal surface.
3. The fact that kinetic energy of the emitted electrons is independent of the intensity of light and depends upon its frequency. Thus, the photoelectric effect cannot be explained on the basis of wave nature of light.

(b) Photon picture of electromagnetic radiation on which Einstein’s photoelectric equation is based on particle nature of light. Its basic features are :

1. In interaction with matter, radiation behaves as if it is made up of particles called photons.
2. Each photon has energy (E = hv), momentum (p =hv /c) , and speed c, the speed of light.
3. All photons of light of a particular frequency v, or wavelength X, have the same energy
   
4. By increasing the intensity of light of given wavelength, there is only an increase in the number of photons per second crossing a given area, with each photon having the same energy. Thus, photon energy is independent of intensity’ of radiation.
5. Photons are electrically neutral and are not deflected by electric and magnetic fields.
6. In a photon – particle collision (such as photon-electron collision), the total energy and total momentum are conserved. However, number of photons may not be conserved.

Answer 18.
(i) Initial voltage, V₁, = V volts and charge stored, Q₁ = 360 μC
Q₁ = CV₁            ………(1)
Changed potential,
V₂ = V -120
Q₂ = 120 μC
Q₂ = CV₂       ………. (2)
By dividing (1) by (2), we get

(ii) If the voltage applied had increased by 120 V, then
V₃ =180 + 120 = 300 V
Hence, charge stored in the capacitor,
Q₃ = CV₃  = 2 x 10^-6  x300 = 600 μC

OR

(i) Given,

Answer 19.


Which shows that the density is independent of mass number A.

Answer 20.
Three important factors which justify the need of modulating a message signal :

(i) Size of antenna or aerial :
For communication within the effective length of the antennas, the transmitting frequencies should be high, so modulation is required.
(ii) Effective power which is radiated by antenna :
Since the power radiated from a linear antenna is inversely proportional to the square of the transmitting wavelength. As high powers are needed for good transmission, so higher frequency is required which can be achieved by modulation.
(iii) The interference of signals from different transmitters :
To avoid the interference of the signals there is a need of high frequency which can be achieved by the modulation.

Answer 21.
Suppose the length of the rod is greater than the radius of the circle and rod rotates anticlockwise and suppose the direction of electrons in the rod at any instant be along +y direction. Suppose the direction of the magnetic field is along +z direction.
Then, using Lorentz law, we get the following :

Thus, the direction of force on the electrons is along x-axis. So, the electrons will move towards the centre i.e., the fixed end of the rod. This movement of electrons will result in current and thus it will generate an emf in the rod between the fixed end and the point touching the ring.
Let 0 be the angle between the rod and radius of the circle at any time t.

Answer 22.
(i) Dynamic output resistance is given as :

SECTION : D

Answer 23.

1. It is safer to be inside a car during thunderstorm because the car acts like a Faraday cage.
2. Awareness and humanity
3. Gratitude and obliged
4. Once I came across to a situation where a puppy was shuck in the middle of a busy road during rain and was not able to cross due to heavy flow, so I quickly rushed and helped him.

SECTION : E

Answer 24.
(a) A compound microscope consists of two convex lenses parallel separated by some distance. The lens nearer to the object is called the objective. The lens through which the final image is viewed is called the eyepiece. Magnifying power, when final image is at infinity: The magnification produced by the compound microscope is the product of the magnifications produced by the eyepiece and objective.
M = M_e x M₀       ……… (i)

∴ Where, M_e and M₀ are the magnifying powers of the eyepiece and objective respectively.
If u₍₎ is the distance of the object from the objective and v₀ is the distance of the image from the objective, then the magnifying power of the objective is

Where, h, h’ are object and image heights ; respectively and f₀ is the focal length of the a” objective.
L is the tube length i.e., the distance between the second focal point of the objective and the first focal point of the eyepiece : When the final image is at infinity,

Magnifying power of compound microscope,

OR

(a) Huygens Principle :

• Each point on the primary wavefront acts as a source of secondary wavelets, transferring out disturbance in all directions in the same way as the original source of light does.
• The new position of the wavefront at any instant is the envelope of the secondary wavelets at that instant.Refraction on the basis of wave theory
• Consider any point Q on the incident wave front.
• Suppose when disturbance from point P on incident wave front reaches point P’ on the refracted wavefront, the disturbance from point Q reaches Q’ on the refracting surface XY.

Since P’A’ represents the refracted wavefront, the time taken by light to travel from a point on incident wavefront to the corresponding point on refracted wavefront should always be the same. Now, time taken by light to go from Q to Q’ will be

This is the Snell’s law for refraction of light.

(b)

1. The frequency of reflected and refracted light remains constant as the frequency of incident light only depends on the source of light.
2. Since the frequency remains same, hence there is no reduction in energy.

Answer 25.

(a) Working principle of Potentiometer :
When a constant current is passed through a wire of uniform area of cross-section, the potential drop across any portion of the wire is directly proportional to the length of that portion.

Applications of Potentiometerfor comparing emfs of two cells :
The following figure shows an application of the potentiometer to compare the emf of two cells of emf E₁ and E,. 1, 2, 3 form a two way key.
When 1 and 3 are connected, E₁ is connected to the galvanometer (G). Jockey is moved to N₁ which is at a distance l₁ from A, to find the balancing length. Applying loop rule to AN₁G31 A,

Thus, we can compare the emfs of any two sources. Generally, one of the cells is chosen as a standard cell whose emf is known to a high degree of accuracy. The emf of the other cell is then calculated from equation (3).

(b)

1. The emf of the cell connected in main circuit may not be more than the emf of the primary cells whose emfs are to be compared.
2. The positive ends of all cells are not connected to the same end of the wire.

OR

(a) Kirchhoff’s First Law – Junction Rule :
The algebraic sum of the currents meeting at a point in an electrical circuit is always zero.
Let the currents be I₁  , I_{2 ,} I₃ and I₄

Convention :
Current towards the junction – positive Current away from the junction – negative
I₃+ (- I₁) + (- I₂) +(- I₄) = 0

Kirchhoff’s Second Law – Loop Rule :
In a closed loop, the algebraic sum of the emfs is equal to the algebraic sum of the products of the resistance and current flowing through them.

For closed part BACB,
E₁ + E₂  =  I₁ R₁– I₃ R₃  + I₂ R₂
For closed part CADC,
E₂ =  I₃ R₃   + I₄ R₄   + I₅ R5

(b) Considering both the situations and writing them in the form of equations. Let R’ be the resistance per unit lenght of the potentiometer wire,

Answer 26.
(a) Consider a rectangular loop-ABCD carrying current I.

Case I :
The rectangular loop is placed such that the uniform magnetic field B is in the plane of loop. No force is exerted by the magnetic field on the arms AD and BC. Magnetic field exerts a force
∴  F₁ = IbB  = F₁
Magnetic field exerts a force F₂ on arm CD.
F₂ = IbB = F₁

Net force on the loop is zero.
The torque on the loop rotates the loop in anti-clockwise direction.

τ = BIA
If there are n such turns the torque will be nIAB
Where, b →Breadth of the rectangular coil
a → Length of the rectangular coil
A = ab → Area of the coil.

Case II :

Plane of the loop is not along the magnetic field, but makes angle with it. Angle between the field and the normal is θ. Forces on BC and DA are equal and opposite and they cancel each other as they are collinear. Force on AB is F, and force on CD is F₂.
F₁= F₂ = IbB

Where A = ab
(b) We know, Lorentz force, F = Bqv sin θ
Where θ = angle between velocity of particle and magnetic field = 90
So, Lorentz force, F = Bqv
Thus, the particles will move in circular path.

Let m_p = mass of proton, m_d = mass of deuteron, v = velocity of proton and v_d = velocity of deuteron The charge of proton and deuteron are equal.

As (1) and (2) are equal, so Thus, the trajectory of both the particles will be same.

OR

(a) The torque on the needle is τ = m x B In magnitude, τ= mB sin θ
Here τ is restoring torque and 0 is the angle between m and B.

Negative sign with mB sin θ implies that restoring torque is in opposition to deflecting torque. For small values of 0 in radians, we approximate sin θ = θ and get