CBSE Physics Sample Papers and Syllabus for Class 12th

CBSE 10th Date sheet 2021 CBSE 12th Date Sheet 2021

SECTION A

This section consists of 25 multiple choice questions with overall choice to attempt any 20 questions. In case more than desirable numberof questions are attempted, ONLY first 20 will be considered for evaluation.

1. Which of the following is NOT the property of equipotential surface?

They do not cross each other.
The rate of change of potential with distance on them is zero.
For a uniform electric field they are concentric spheres.
They can be imaginary spheres.

The correct answer is For a uniform electric field they are concentric spheres.

2. Two point charges +8q and -2q are located at x=0 and x=L respectively. The point on x axis at which net electric field is zero due to these charges is-

8L
4L
2 L
L

The correct answer is 2 L.

3. An electric dipole of moment p is placed parallel to the uniform electric field. The amount of work done in rotating the dipole by 900 is-

2pE
pE
pE/2
Zero

The correct answer is pE

4. Three capacitors 2µF, 3µF and 6µF are joined in series with each other. The equivalent capacitance is-

1/2µF
1µF
2µF
11µF

The correct answer is 11µF

5. Two point charges placed in a medium of dielectric constant 5 are at a distance r between them, experience an electrostatic force ‘F’. The electrostatic force between them in vacuum at the same distance r will be-

5F
F
F/2
F/5

The correct answer is 5F

6. Which statement is true for Gauss law-

All the charges whether inside or outside the gaussian surface contribute to the electric flux.
Electric flux depends upon the geometry of the gaussian surface.
Gauss theorem can be applied to non-uniform electric field.
The electric field over the gaussian surface remains continuous and uniform at every point.

The correct answer is The electric field over the gaussian surface remains continuous and uniform at every point.

7. A capacitor plates are charged by a battery with ‘V’ volts. After charging battery is disconnected and a dielectric slab with dielectric constant ‘K’ is inserted between its plates, the potential across the plates of a capacitor will become

Zero
V/2
V/K
KV

The correct answer is V/K

8. The best instrument for accurate measurement of EMF of a cell is-

Potentiometer
metre bridge
Voltmeter
ammeter and voltmeter

The correct answer is Potentiometer

9. An electric current is passed through a circuit containing two wires of same material, connected in parallel. If the lengths and radii of the wires are in the ratio of 3:2 and 2:3, then the ratio of the current passing through the wire will be

2:3
3:2
8:27
27:8

The correct answer is 8:27

10. By increasing the temperature, the specific resistance of a conductor and a semiconductor-

increases for both.
decreases for both.
increases for a conductor and decreases for a semiconductor.
decreases for a conductor and increases for a semiconductor.

The correct answer is increases for a conductor and decreases for a semiconductor.

11. We use alloys for making standard resistors because they have

low temperature coefficient of resistivity and high specific resistance
high temperature coefficient of resistivity and low specific resistance
low temperature coefficient of resistivity and low specific resistance
high temperature coefficient of resistivity and high specific resistance

The correct answer is low temperature coefficient of resistivity and high specific resistance.

12. A constant voltage is applied between the two ends of a uniform metallic wire, heat ‘H’ is developed in it. If another wire of the same material, double the radius and twice the length as compared to original wire is used then the heat developed in it will be-

H/2
H
2H
4H

The correct answer is 2H

13. If the potential difference V applied across a conductor is increased to 2V with its temperature kept constant the drift velocity of the free electrons in a conductor will -

remain the same
become half of its previous value
be double of its initial value
become zero.

The correct answer is become half of its previous value.

14. The equivalent resistance between A and B is-

3 ohms
5.5 ohms
7.5 ohms
9.5 ohms

The correct answer is 7.5 ohms

15. The SI unit of magnetic field intensity is

AmN-1
NA-1m-1
NA-2m-2
NA-1m-2

The correct answer is NA-1m-1

16. The coil of a moving coil galvanometer is wound over a metal frame in order to

reduce hysteresis
increase sensitivity
increase moment of inertia
provide electromagnetic damping

The correct answer is provide electromagnetic damping

17. Two wires of the same length are shaped into a square of side 'a' and a circle with radius 'r'. If they carry same current, the ratio of their magnetic moment is

2 : π
π : 2
π : 4
4 : π

The correct answer is π : 4

18. The horizontal component of earth’s magnetic field at a place is √3 times the vertical component. The angle of dip at that place is

π/6
π/3
π/4
0

The correct answer is π/6.

19. The small angle between magnetic axis and geographic axis at a place is-

Magnetic meridian
Geographic meridian
Magnetic inclination
Magnetic Declination

The correct answer is Magnetic Declination.

20. Two coils are placed close to each other. The mutual inductance of the pair of coils depends upon the

rate at which current change in the two coils
relative position and orientation of the coils
rate at which voltage induced across two coils
currents in the two coils

The correct answer is relative position and orientation of the coils.

21. A conducting square loop of side 'L' and resistance 'R' moves in its plane with the uniform velocity 'v' perpendicular to one of its sides. A magnetic induction 'B' constant in time and space pointing perpendicular and into the plane of the loop exists everywhere as shown in the figure. The current induced in the loop is

BLv/R Clockwise
BLv/R Anticlockwise
2BLv/R Anticlockwise
Zero

The correct answer is Zero

22. The magnetic flux linked with the coil (in Weber) is given by theequation – Փ = 5t2 + 3t + 16 The induced EMF in the coil at time, t=4 will be-

-27 V
-43 V
-108 V
210 V

The correct answer is -43 V

23. Which of the following graphs represent the variation of current(I) with frequency (f) in an AC circuit containing a pure capacitor?

The correct answer is iii.

24. A 20 volt AC is applied to a circuit consisting of a resistance and a coil with negligible resistance. If the voltage across the resistance is 12 volt, the voltage across the coil is-

16 V
10 V
8 V
6 V

The correct answer is 16 V

25. The instantaneous values of emf and the current in a series ac circuit are- E = Eo Sin ωt and I= Io sin( ωt+π/3) respectively, then it is

Necessarily a RL circuit
Necessarily a RC circuit
Necessarily a LCR circuit
Can be RC or LCR circuit

The correct answer is Can be RC or LCR circuit.

SECTION B

This section consists of 24 multiple choice questions with overall choice to attempt any 20 questions. In case more than desirable number of questions are attempted, ONLY first 20 will be considered for evaluation.

26. A cylinder of radius r and length l is placed in an uniform electric field parallel to the axis of the cylinder. The total flux for the surface of the cylinder is given by-

zero
π r2
E π r2
2 Eπ r2

The correct answer is zero.

27. Two parallel large thin metal sheets have equal surface densities 26.4x10-12 C/m2 of opposite signs. The electric field between these sheets is-

1.5N/C
1.5 x 10-16 N/C
3 x 10-10N/C
3N/C

The correct answer is 3N/C.

28. Consider an uncharged conducting sphere. A positive point charge is placed outside the sphere. The net charge on the sphere is then,

negative and uniformly distributed over the surface of sphere
positive and uniformly distributed over the surface of sphere
negative and appears at a point the surface of sphere closest to point charge.
Zero

The correct answer is Zero.

29. Three Charges 2q, -q and -q lie at vertices of a triangle. The value of E and V at centroid of triangle will be-

E#0 and V#0
E=0 and V=0
E#0 and V=0
E=0 and V#0

The correct answer is E#0 and V=0.

30. Two parallel plate capacitors X and Y, have the same area of plates and same separation between plates. X has air and Y with dielectric of constant 2 , between its plates. They are connected in series to a battery of 12 V. The ratio of electrostatic energy stored in X and Y is-

4:1
1:4
2:1
1:2

The correct answer is 2:1

31. Which among the following, is not a cause for power loss in a transformer-

Eddy currents are produced in the soft iron core of a transformer.
Electric Flux sharing is not properly done in primary and secondary coils.
Humming sound produed in the tranformers due to magnetostriction.
Primary coil is made up of a very thick copper wire.

The correct answer is Primary coil is made up of a very thick copper wire.

32. An alternating voltage source of variable angular frequency ‘w’ and fixed amplitude ‘V’ is connected in series with a capacitance C and electric bulb of resistance R(inductance zero). When ‘w’ is increased-

The bulb glows dimmer.
The bulb glows brighter.
Net impedance of the circuit remains unchanged.
Total impedance of the circuit increases.

The correct answer is The bulb glows brighter.

33. A solid spherical conductor has charge +Q and radius R. It is surrounded by a solid spherical shell with charge -Q, innerradius 2R, and outer radius 3R. Which of the following statements is true?

The electric potential has a maximum magnitude at C and the electric field has a maximum magnitude at A
The electric potential has a maximum magnitude at D and the electric field has a maximum magnitude at B.
The electric potential at A is zero and the electric field has a maximum magnitude at D.
Both the electric potential and electric field achieve a maximum magnitude at B.

The correct answer is Both the electric potential and electric field achieve a maximum magnitude at B.

34. A battery is connected to the conductor of non-uniform cross section area. The quantities or quantity which remains constant is-

electric field only
drift speed and electric field
electric field and current
current only

The correct answer is current only

35. Three resistors having values R battery. Suppose R1 carries a current of 2.0 A, R ohms, and R3 dissipates 6.0 watts of power. Then the voltage across R is-

1V
2V
3V
4V

The correct answer is 3V

36. A straight line plot showing the terminal potential difference (V) of a cell as a function of current (I) drawn from it, is internal resistance of the cell would be then

2.8 ohms
1.4 ohms
1.2 ohms
zero

The correct answer is 2.8 ohms

37. A 10 m long wire of uniform cross-section and 20 Ω resistance is used in a potentiometer. The wire is connected in series with a battery of 5 V along with an external resistance of 480 Ω. If an unknown emf E is balanced at 6.0 m length of the wire then the value of unknown emf is

1.2 V
1.02 V
0.2 V
0.12 V

The correct answer is 0.12 V.

38. The current sensitivity of a galvanometer increases by 20%. If its resistance also increases by 25%, the voltage sensitivity will

decrease by 1%
increased by 5%
increased by 10%
decrease by 4%

The correct answer is decrease by 4%.

39. Three infinitely long parallel straight current carrying wires A, B and C are kept at equal distance from each other as shown in the figure . The wire C experiences net force F .The net force on wire C, when the current in wire A is reversed will be

Zero
F/2
F
2F

The correct answer is Zero.

40. In a hydrogen atom the electron moves in an orbit of radius 0.5 Ao making 10 revolutions per second, the magnetic moment associated with the orbital motion of the electron will be

2.512 x 10-38 Am2
1.256 x 10-38 Am2
0.628 X10-38 Am2
zero

The correct answer is 1.256 x 10-38 Am2

41. An air-cored solenoid with length 30 cm, area of cross-section 25 cm2 and number of turns 800, carries a current of 2.5 A. The current is suddenly switched off in a brief time of 10-3s. Ignoring the variation in magnetic field near the ends of the solenoid, the average back emf induced across the ends of the open switch in the circuit would be

zero
3.125 volts
6.54 volts
16.74 volts

The correct answer is 3.125 volts

42. A sinusoidal voltage of peak value 283 V and frequency 50 Hz is applied to a series LCR circuit in which R = 3 Ω, L = 25.48 mH, and C = 796 µF, then the power dissipated at the resonant condition will be-

39.70 kW
26.70 kW
13.35 kW
13.35 kW

The correct answer is 13.35 kW

43. A circular loop of radius 0.3cm lies parallel to much bigger circular of radius 20 cm. The centre of the small loop is on the axis of the bigger loop. The distance between their centres is 15 cm. If a current of 2.0 A flows through the smaller loop, then the flux linked with the bigger loop is

3.3 X 10-11weber
6 X 10-11weber
6.6 X 10-9weber
9.1 X 10-11weber

The correct answer is 9.1 X 10-11weber.

44. If both the number of turns and core length of an inductor is doubled keeping other factorsconstant, then its self-inductance will be-

Unaffected
doubled
halved
quadrupled

The correct answer is doubled

45. Given below are two statements labelled as Assertion (A) and Reason (R)

Assertion (A): To increase the range of an ammeter, we must connect a suitable high resistance in series to it.

Reason (R): The ammeter with increased range should have high resistance.