CBSE Physics Class 12 Sample Paper 14 Page 1

Sample Paper 14
Class XII 2024-25
Physics
Time: 3 Hours Max. Marks: 70
General Instructions:
1. There are 33 questions in all. All questions are compulsory.
2. This question paper has five sections: Section A, Section B, Section C, Section D and Section E.
3. All the sections are compulsory.
4. Section A contains sixteen questions, twelve MCQ and four assertion reasoning based of 1 mark each,
Section B contains five questions of 2 marks each, Section C contains seven questions of 3 marks each,
Section D contains two case study based questions of 4 marks each and Section E contains three long
questions of 5 marks each.
5. There is no overall choice. However, an internal choice has been provided in one question in Section B,
one question in Section C, one question in each CBQ in Section D and all three questions in Section E.
You have to attempt only one of the choices in such questions
6. Use of calculators is not allowed.
7. You may use the following values of physical constants where ever necessary
i. c = 3 # 108 m/s
ii. me = 9.1 # 10−31 kg
iii. e = 1.6 # 10−19 C
iv. µ 0 = 4π # 10−7 TmA−1
v. h = 6.63 # 10−34 Js
vi. ε 0 = 8.854 # 10−12 C2 N−1 m−2
vii. Avogadro’s number = 6.023 # 1023 per gram mole

SECTION-A
1. Which element is used in electric heater?
(a) Copper (b) Platinum
(c) Tungsten (d) Nichrome

2. S.I. unit of magnetic moment is

(a) JT-2 (b) Am2
(c) JT (d) Am-1

3. Which of the following ratios is constant for an isolated conductor?

Total charg e Ch arge added
(a) (b)
Potential Potential difference
(Total charg e) 2
(c) (d) none of these
Potential

4. If the kinetic energy of an electron doubles, its de-Broglie’s wavelength changes by a factor
(a) 2 (b) 2
(c) 1 (d) 1
2 2

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5. Which of the following rays are not electromagnetic waves ?

(a) γ -rays (b) β -rays
(c) X-rays (d) heat rays

6. The electrostatic field is

(a) conservative (b) non-conservative
(c) both (a) and (b) (d) none of these

7. In Young’s double slit experiment, if one slit is covered with red filter and the other slit is covered by green
filter, then their interference pattern will be
(a) red (b) green
(c) yellow (d) invisible

8. In an AC circuit containing only capacitor, the current

(a) leads the voltage by 90c (b) leads the voltage by 180c
(c) lags behind the voltage by 90c (d) remains in phase with the voltage

9. An object is placed at a distance f in the front of a convex mirror. If focal length of the mirror is f , then
distance of image from pole of the mirror is
(a) f (b) 2f
f f
(c) (d)
2 4

10. The Lenz’s law gives

(a) direction of induced E.M.F. (b) magnitude of induced E.M.F.
(c) direction of induced current (d) magnitude of induced current

11. For an electron in the second orbit of Bohr’s hydrogen atom, the moment of liner momentum is
(a) πh (b) 2πh
(c) h (d) 2h
π π

12. Two equal electric currents are flowing perpendicular to each other as shown in the figure. AB and CD
are perpendicular to each other and symmetrically placed with respect to the currents. Where do we
expect the resultant magnetic field to be zero ?

(a) on AB (b) on CD
(c) on both AB and CD (d) on both OD and BO

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13. Assertion : Microwaves are better carrier of signals than optical waves.
Reason : Microwaves move faster than optical waves.
(a) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(b) Both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
(c) Assertion is correct but Reason is incorrect.
(d) Assertion is incorrect but Reason is correct.

14. Assertion : By roughening the surface of a glass sheet its transparency can be reduced.
Reason : Glass sheet with rough surface absorbs more light.
(a) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(b) Both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
(c) Assertion is correct but Reason is incorrect.
(d) Assertion is incorrect but Reason is correct.

15. Assertion : No interference pattern is detected when two coherent sources are infinitely close to each other.
Reason : The fringe width is inversely proportional to the distance between the two slits.
(a) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(b) Both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
(c) Assertion is correct but Reason is incorrect.
(d) Assertion is incorrect but Reason is correct.

16. Assertion (A) : The whole charge of a conductor cannot be transferred to another isolated conductor.
Reason (R) : The total transfer of charge from one to another is not possible.
(a) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(b) Both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
(c) Assertion is correct but Reason is incorrect.
(d) Assertion is incorrect but Reason is correct.

SECTION-B
17. Identify the part of the electromagnetic spectrum which is
(a) suitable for radar system used in aircraft navigation.
(b) produced by bombarding a metal target by high speed electrons

18. In a certain 0.5 cm3 of space, electric potential is found to be 7 V throughout. What is the electric field
in this region ?

19. Plot a graph showing variation of photoelectric current with collector plate potential at a given frequency
and intensity of incident radiation. What does the intercept of the graph with potential axis signify?


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What is meant by work function of a metal? How does the value of work function influence the kinetic
energy of electrons liberated during photoelectron emission?

20. The relative magnetic permeability of a magnetic material is 800. Identify the nature of magnetic material
and state its two properties.

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21. The charging current for a capacitor is 0.25 A. What is the displacement current across its plates?

SECTION-C
22. (a) Why are coherent sources necessary to produce a sustained interference pattern ?
(b) In Young’s double slit experiment using monochromatic light of wavelength λ , the intensity of light
at a point on the screen where path difference is λ is K units. Find out the intensity of light at a
point where path difference is λ/3.

23. Define ionization energy. How would the ionization energy change when electron in hydrogen atom is
replaced by a particle of mass 200 times that of the electron but having the same charge?

24. The V - I characteristic of a silicon diode is as shown in the figure. Calculate the resistance of the diode at
1. I = 15 mA
2. V =− 10 V .

25. (a) State clearly how a microwave oven works to heat up a food item containing water molecules.
(b) Why are microwaves found useful for the RADAR systems in aircraft navigation ?


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(i) Which segment of electromagnetic waves has highest frequency ? How are these waves produced ?
Give one use of these waves.
(ii) Which electromagnetic waves lie near the high frequency one of visible part of electromagnetic
spectrum ? Give its one use. In what way this component of light has harmful effects on human ?

26. Show with the help of a diagram, how the force between the two conductors would change when the
currents in them flow in the opposite directions.

27. State Faraday’s laws of electromagnetic induction. Express them mathematically.

28. Derive an expression for the torque experienced by electric dipole in external electric field.

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SECTION-D

Case Study Based Questions.

Read the following paragraph and answer the questions that follow.

29. The electron mobility characterises how quickly an electron can move through a metal of semiconductor
when pulled by an electric field. There is an analogous quality for holes, called hole mobility. A block of
pure silicon at 300 K has a length of 10 cm and an area of 1.0 cm2. A battery of emf 2 V is connected across
it. The mobility of electron is 0.14 m2 V-1 s-1 and their number density is 1.5 # 1016 m-3 . The mobility of
holes is 0.05 m2 V-1 s-1 .
(i) The electron current is
(a) 6.72 # 10-4 A (b) 6.72 # 10-5 A
(c) 6.72 # 10-6 A (d) 6.72 # 10-7 A
(ii) The hole current is
(a) 2.0 # 10-7 A (b) 2.2 # 10-7 A
(c) 2.4 # 10-7 A (d) 2.6 # 10-7 A

(iii) The number density of donor atoms which are to be added up to pure silicon semiconductor
to produce an n-type semiconductor of conductivity 6.4 Ω−1 cm−1 is approximately (neglect the
contribution of holes to conductivity)
(a) 3 # 1022 m-3 (b) 3 # 1023 m-3
(c) 3 # 1024 m-3 (d) 3 # 1021 m-3

(iv) When the given silicon semiconductor is doped with indium, the hole concentration increases to
4.5 # 1023 m-3 . The electron concentration in doped silicon is
(a) 3 # 109 m-3 (b) 4 # 109 m-3
(c) 5 # 109 m-3 (d) 6 # 109 m-3


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(v) Pick out the statement which is not correct.
(a) At a low temperature, the resistance of a semiconductor is very high.
(b) Movement of holes is restricted to the valence band only.
(c) Width of the depletion region increases as the forward bias voltage increases in case of a p-n
junction diode.
(d) In a forward bias condition, the diode heavily conducts.

30. A prism is a portion of a transparent medium bounded by two plane faces inclined to each other at
a suitable angle. A ray of light suffers two refractions on passing through a prism and hence deviates
through a certain angle from its original path. The angle of deviation of a prism is, δ = ^µ − 1h A , through
which a ray deviates on passing through a thin prism of small refracting angle A. If µ is refractive index
sin ^A + δ m h /2
of the material of the prism, then prism formula is, µ =
sin A/2
(i) For which colour, angle of deviation is minimum?
(a) Red (b) Yellow
(c) Violet (d) Blue
(ii) When white light moves through vacuum
(a) all colours have same speed (b) different colours have different speeds
(c) violet has more speed than red (d) red has more speed than violet.

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(iii) The deviation through a prism is maximum when angle of incidence is

(a) 45° (b) 70°
(c) 90° (d) 60°

(iv) What is the deviation produced by a prism of angle 6°? (Refractive index of the material of the
prism is 1.644).
(a) 3.864° (b) 4.595°
(c) 7.259° (d) 1.252°

(v) A ray of light falling at an angle of 50° is refracted through a prism and suffers minimum deviation.
If the angle of prism is 60°, then the angle of minimum deviation is
(a) 45° (b) 75°
(c) 50° (d) 40°

SECTION-E
31. State the working of AC generator with the help of a labelled diagram.
The coil of an AC generator having N turns, each of area A, is rotated with a constant angular velocity
ω Deduce the expression for the alternating emf generated in the coil.
What is the source of energy generation in this device?


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Draw a labelled diagram of a step-down transformer. State the principle of its working. Express the turn
ratio in terms of voltages.
Find the ratio of primary and secondary currents in terms of turn ratio in an ideal transformer.
How much current is drawn by the primary of a transformer connected to 220 V supply when it delivers
power to a 100 V - 500 W refrigerator?

32. For a nuclear reaction A + b " c + d , the Q -value is defined as Q [mA - mb - md ] c2 . A radioactive nuclear
11 +
6 C " 5 B + e + v ; T1/2
11 = 20.3 minutes. The maximum energy emitted by positron is 0.960 MeV. following
values are given-
m^116 C h = 11.011434u , m^115 B h = 11.009305u, mc = 0.000548u . Evaluate Q -value of this reaction and
compare it with maximum Energy Emitted by Positron.


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(i) Write three characteristic properties of nuclear force.
(ii) Draw a plot of potential energy of a pair of nucleons as a function of their separation. Write two
important conclusions that can be drawn from the graph.

33. 1. Obtain the formula for the power loss (i.e. power dissipated) in a conductor of resistance R carrying
a current.
2. Two heating elements of resistances R1 and R2 when operated at a constant supply of voltage V ,
consume powers P1 and P2 , respectively. Deduce the expressions for the power of their combination
when they are in turn, connected in
(a) Series and
(b) Parallel across their same voltage supply.


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Use Kirchhoff’s laws to determine the value of current I1 in the given electrical circuit.

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