# CBSE Class 12 Physics MCQ With Answer

### NCERT, CBSE Class 12 PHYSICS MCQ Questions with Answers

NCERT, CBSE Class 12 PHYSICS MCQ Questions with Answers, CLASS 12 PHYSICS PER TEST UT 1 EXAMINATION, Class 12 Online Quiz MCQ Questions free Download, Class 12 PHYSICS Online Exam MCQ Quiz, Class 12 MCQ Questions with Answers for all Subject, Mcq Questions With Answers of Class 12 PHYSICS, Multiple Choice Questions for Class 12 PHYSICS, Class 12 Multiple Choice Questions with Answers

1. Two similar spheres having +Q and -Q charges are kept at a certain distance. F force acts between the two. If at the middle of two spheres, another similar sphere having +Q charge is kept, then it experiences a force in magnitude and direction as

(a) zero having no direction.

(b) 8F towards +Q charge.

(c) 8F towards -Q charge

(d) 4F towards +Q charge

2.. A charge Q is divided into two parts of q and Q – q. If the coulomb repulsion between them when they are separated is to be maximum, the ratio of Q/q should be

(a) 2:1

b) 1/2

(c) 4:1

(d) 1/4

3. The electric field inside a spherical shell of uniform surface charge density is

(a) zero.

(b) constant, less than zero.

(c) directly proportional to the distance from the centre.

(d) none of the these

4.The electric field intensity due to an infinite cylinder of radius R and having charge q per unit length at a distance rir r(r > R) from its axis is

(a) directly proportional to r².

(b) directly proportional to r3.

(c) inversely proportional to r.

(d) inversely proportional to r².

5. A charge Q is placed at the centre of the line joining two point charges +q and +q as shown in the figure. The ratio of charges Q and q is

(a) 4

(b) 1/4

(c) -4

(d) -1/4

6.The total flux through the faces of the cube with side of length a if a charge q is placed at corner A of the cube is

a.q/8ε0

b.q/4ε0

c. q/ε0

d.q/2ε0

7.Consider a region inside which, there are various types of charges but the total charge is zero. At points outside the region

(a) the electric field is necessarily zero.

(b) the electric field is due to the dipole moment of the charge distribution only.

(c) the dominant electric field is inversely pro-portional to r3, for large r (distance from ori-gin).

(d) the work done to move a charged particle along a closed path, away from the region will not be zero.

8.. Four charges are arranged at the comers of a square ABCD, as shown. The force on the charge kept at the centre O is

(a) zero

(b) along the diagonal AC

(c) along the diagonal BD

(d) perpendicular to side AB

9.A positively charged particle is released from rest in an uniform electric field. The electric potential energy of the charge

(a) remains a constant because the electric field is uniform.

(b) increases because the charge moves along the electric field.

(c) decreases because the charge moves along the electric field.

(d) decreases because the charge moves opposite to the electric field.

10.. Equipotentials at a great distance from a collection of charges whose total sum is not zero are approximately

(a) spheres

(b) planes

(c) paraboloids

(d) ellipsoids

11. Two small spheres each carrying a charge q are placed r metre apart. If one of the spheres is taken around the other one in a circular path of radius r, the work done will be equal to

(a) force between them × r

(b) force between them × 2πr

(c) force between them/2πr

(d) zero

12.If a unit positive charge is taken from one point to another over an equipotential surface, then

(a) work is done on the charge.

(b) work is done by the charge.

(c) work done is constant.

(d) no work is done

13.. A hollow metal sphere of radius 5 cm is charged so that the potential on its surface is 10 V. The potential at the centre of the sphere is

(a) 0 V

(b) 10 V

(c) Same as at point 5 cm away from the surface

(d) Same as at point 25 cm away from the surface

14.A capacitor is charged by a battery. The battery is removed and another identical uncharged capacitor is connected in parallel. The total electrostatic energy of resulting system

(a) increases by a factor of 4.

(b) decreases by a factor of 2.

(c) remains the same.

(d) increases by a factor of 2.

15.Figure shows the electric lines of force emerging from a charged body. If the electric field at A and B are EA and EB respectively and if the displacement between A and B is r then

(a) EA > EB

(b) EA < EB

(c) EA = EB/r

(d) EA = EB /r²

16. A parallel plate condenser is connected with the terminals of a battery. The distance between the plates is 6mm. If a glass plate (dielectric constant K = 9) of 4.5 mm is introduced between them, then the capacity will become

(a) 2 times

(b) the same.

(c) 3 times.

(d) 4 times

17. Three charges Q, +q and +q are placed at the vertices of an equilateral triangle of side l as shown in the figure. If the net electrostatic energy of the system is zero, then Q is equal to

(a) -q

(b) +q

(c) zero

(d) –$frac{q}{2}$

18. Two metal plates form a parallel plate capacitor. The distance between the plates is d. A metal sheet of thickness  $frac{d}{2}$  and of the same area is introduced between the plates.
What is the ratio of the capacitance in the two cases?

(a) 2 : 1

(b) 3 : 1

(c) 2 : 1

(d) 5 : 1

19. Acapacitor of 4 pF is connected as shown in the circuit. The internal resistance of the battery is 0.5 Q. The amount of charge on the capacitor plates will be [NCERT Exemplar]

(a) 0

(b) 4

(c) 16 μC

(d) 8 μC

20. A capacitor is charged by using a battery which is then disconnected. A dielectric slab
then slipped between the plates, which results in

(a) reduction of charge on the plates and increase of potential difference across the plates.

(b) increase in the potential difference across the plate, reduction in stored energy, but no change in the charge on the plates.

(c) decrease in the potential difference across the plates, reduction in the stored energy, but no change in the charge on the plates.

(d) none of these

21. Which of the following statement is true?

(a) Electrostatic force is a conservative force.

(b) Potential at a point is the work done per unit charge in bringing a charge from any point to infinity.

(c) Electrostatic force is non-conservative

(d) Potential is the product of charge and work.

22. An electric dipole of moment $vec{p}$ is placed in a uniform electric field $vec{E}$ . Then
(i) the torque on the dipole is $vec{p} imes overrightarrow{mathrm{E}}$
(ii) the potential energy of the system is $vec{p} . overrightarrow{mathrm{E}}$
(iii) the resultant force on the dipole is zero. Choose the correct option.

(a) (i), (ii) and (iii) are correct

(b) (i) and (iii) are correct and (ii) is wrong

(c) only (i) is correct

(d) (i) and (ii) are correct and (iii) is wrong

23  When air is replaced by a dielectric medium of constant K, the maximum force of attraction between two charges separated by a distance

(a) increases K times

(b) remains unchanged

(c) decreases K times

(d) increases K-1 times

24.. Two identical capacitors are joined in parallel, charged to a potential V, separated and then connected in series, the positive plate of one is connected to the negative of the other. Which of the following is true?

(a) The charges on the free plated connected to-gether are destroyed.

(b) The energy stored in ths system increases.

(c) The potential difference between the free plates is 2V.

(d) The potential difference remains constant.

25.Two spherical conductors each of capacity C are charged to potential V and -V. These are then connected by means of a fine wire. The loss of energy is

(a) zero

(b) 1/2CV2

(c) CV2

(d) 2 CV2

26. A parallel plate air capacitor is charged to a potential difference of V volts. After disconnecting the charging battery the distance between the plates of the capacitor is increased using an insulating handle. As a result the potential difference between the plates

(a) increases

(b) decreases

(c) does not change

(d) becomes zero

27.Which of the following statements is false for a perfect conductor?

(a) The surface of the conductor is an equipoten-tial surface.

(b) The electric field just outside the surface of a conductor is perpendicular to the surface.

(c) The charge carried by a conductor is always uniformly distributed over the surface of the conductor.

(d) None of these.

27. Consider a current carrying wire current I in the shape of a circle. Note that as the current progresses along the wire, the direction of j (current density) changes in an exact manner, while die current/remain unaffected. The agent that is essentially responsible for is

(a) source of emf.

(b) electric field produced by charges accumulated on the surface of wire.

(c) the charges just behind a given segment of wire which push them just the right way by repulsion.

28. Two batteries of ε1 and ε2 (ε2 > ε1) and internal resistance r1 and r2 respectively are connected in parallel as shown in figure. [NCERT Exemplar]

(a ) The equivalent emf εeq of the two cells is between ε1 and ε2 i.e. ε1 < εeq < ε2.

(b) The equivalent emf εeq is smaller than ε1.

(c) The eeq is given by εeq= ε1 + ε2 always.

(d) zeq is independent of internal resistances r1 and r2

29. A resistance R is to be measured using a meter bridge. Student chooses the standard resistance S to be 100 Ω He finds the null point at l1 = 2.9 cm. He is told to attempt to improve the accuracy. Which of the following is a useful way?

(a) He should measure l1 more accurately.

(b) He should change Sto 1000 Ω and repeat the experiment.

(c) He should change S to 3 Ω and repeat the experiment.

(d) He should give up hope of a more accurate measurement with a meter bridge.

30.Two cells of emf’s approximately 5 V and 10 V are to be accurately compared using a potentiometer of length 400 cm

(a) The battery that runs the potentiometer should have voltage of 8 V.

(b) The battery of potentiometer can have a voltage of 15 V and R adjusted so that the potential drop across the wire slightly exceeds 10 V.

(c) The first portion of 50 cm of wire itself should have a potential drop of 10 V.

(d) Potentiometer is usually used for comparing resistances and not voltages.

31. In a meter bridge, the point D is a neutral point (figure)

(a) The meter bridge can have other neutral point for this set of resistances.

(b) When the jockey contacts a point on meter wire left of D, current flows to B from the wire.

(c) When the jockey contacts a point on the meter wire to the right of D, current flows from B to the wire through galvanometer.

(d) When R is increased, the neutral point shifts to left

32. Which of the following is wrong? Resistivity of a conductor is

(a) independent of temperature.

(b) inversely proportional to temperature.

(c) independent of dimensions of conductor.

(d) less than resistivity of a semiconductor.

33. For measurement of potential difference, a potentiometer is preferred over voltmeter because

(a) potentiometer is more sensitive than voltmeter.

(b) the resistance of potentiometer is less than voltmeter.

(c) potentiometer is cheaper than voltmeter.

(d) potentiometer does not take current from the circuit.

33.For a cell, the graph between the potential difference (V) across the terminals of the cell and the current (I) drawn from the cell is shown in the figure.

The e.m.f. and the internal resistance of the cell are

(a) 2V, 0.5 Ω

(b) 2V, 0.4 Ω

(c) > 2V, 0.5 Ω

(d) > 2V, 0.4 ?

34.Three resistors each of 2 ohm are connected together in a triangular shape. The resistance between any two vertices will be

(a) 4/3 ohm

(b) 3/4 ohm

(c) 3 ohm

(d) 6 ohm

36.From the graph between current I and voltage V shown below, identify the portion corresponding to negative resistance

(a) AB

(b) BC

(c) CD

(d) DE

37.A charge is moving across a junction, then

(a) momentum will be conserved

(b) momentum will not be conserved

(c) at some places momentum will be conserved and at some other places momentum will not be conserved.

(d) none of these

38.The resistivity of alloy manganin is

(a) Nearly independent of temperature

b) Increases rapidly with increase in temperature

(c) Decreases with increase in temperature

(d) Increases rapidly with decrease in temperature

39. An electric heater is connected to the voltage supply. After few seconds, current gets its steady value then its initial current will be

(a) equal to its steady current

(b) slightly higher than its steady current

(c) slightly less than its steady current

(d) zero

40. Combine three resistors 5 Q, 4.5 Q and 3 Q in such a way that the total resistance of this combination is maximum

(a) 12.5 Q

(b) 13.5 Q

(c) 14.5 Q

(d) 16.5 Q

41. In a Wheatstone bridge if the battery and galvanometer are interchanged then the deflection in galvanometer will

(a) change in previous direction

(b) not change

(c) change in opposite direction

(d) none of these.

42.In a potentiometer of 10 wires, the balance point is obtained on the 7th wire. To shift the balance point to 9th wire, we should

(a) decrease resistance in the main circuit.

(b) increase resistance in the main circuit.

(c) decrease resistance in series with the cell whose emf is to be measured.

(d) increase resistance in series with the cell whose emf is to be determined.

43.AB is a wire of potentiometer with the increase in the value of resistance R, the shift in the balance point J will be

(a) towards B

(b) towards A

(c) remains constant

(d) first towards B then back towards A.

44. The figure below shows currents in a part of electric circuit. The current i is ________ .

a .1.3

b.1.9

c.1.8

d 1.7

45. When a glass rod is rubbed with silk, it

(a) gains electrons from silk.

(b) gives electrons to silk.

(c) gains protons from silk.

(d) gives protons to silk.

46.Two charges of equal magnitudes kept at a distance r exert a force F on each other. If the charges are halved and distance between them is doubled, then the new force acting on each charge is

A F/8

B F/16

C F/4

D F/2

47.. In Fig. (i) two positive charges q2 and q3 fixed along the y-axis, exert a net electric force in the +x direction on a charge q1 fixed along the x-axis. If a positive charge Q is added at (x, 0) in figure (ii), the force on q1 is [NCERT Exemplar]

a) shall increase along the positive x-axis.

(b) shall decrease along the positive x-axis.

(c) shall point along the negative x-axis.

(d) shall increase but the direction changes because of the intersection of Q with q2 and qy

48. SI unit of permittivity of free space is

(b) Weber

(c) C2N-1 m-2

(d) C2N-1 m-2

49. Gauss’s law will be invalid if

(a) there is magnetic monopoles

(b) the inverse square law is not exactly true.

(c) the velocity of light is not a universal constant.

(d) none of these

50  Figures show some equipotential lines distributed in space. A charged object is moved from point A to point B.

(a) The work done in Fig. (i) is the greatest.

(b) The work done in Fig. (ii) is least.

(c) The work done is the same in Fig. (i), Fig.(ii) and Fig. (iii).

(d) The work done in Fig. (iii) is greater than Fig. (ii) but equal to that in Fig. (i).

52. In a meter bridge, the point D is a neutral point (figure). [NCERT Exemplar]

(a) The meter bridge can have other neutral point for this set of resistances.

(b) When the jockey contacts a point on meter wire left of D, current flows to B from the wire.

(c) When the jockey contacts a point on the meter wire to the right of D, current flows from B to the wire through galvanometer.

(d) When R is increased, the neutral point shifts to left.

53.Which of the following is wrong? Resistivity of a conductor is

(a) independent of temperature.

(b) inversely proportional to temperature.

(c) independent of dimensions of conductor.

(d) less than resistivity of a semiconductor.

54. Drift velocity vd varies with the intensity of electric field as per the relation

(a) vd ∝ E

(b) vd ∝ 1/E

(c) vd = constant

(d) vd ∝ E²

55. For a cell, the graph between the potential difference (V) across the terminals of the cell and the current (I) drawn from the cell is shown in the figure.

The e.m.f. and the internal resistance of the cell are

(a) 2V, 0.5 Ω

(b) 2V, 0.4 Ω

(c) > 2V, 0.5 Ω

(d) > 2V, 0.4 Ω

56.Three resistors each of 2 ohm are connected together in a triangular shape. The resistance between any two vertices will be

(a) 4/3 ohm

(b) 3/4 ohm

(c) 3 ohm

(d) 6 ohm

57. The I-V characteristics shown in figure represents

(a) ohmic conductors

(b) non-ohmic conductors

(c) insulators

(d) superconductors

58. Which of the following is wrong? Resistivity of a conductor is

(a) independent of temperature.

(b) inversely proportional to temperature.

(c) independent of dimensions of conductor

d) less than resistivity of a semiconductor.

59.. In parallel combination of n cells, we obtain

(a) more voltage

(b) more current

(c) less voltage

(d) less current

60.. In a potentiometer of 10 wires, the balance point is obtained on the 7th wire. To shift the balance point to 9th wire, we should

(a) decrease resistance in the main circuit.

(b) increase resistance in the main circuit.

(c) decrease resistance in series with the cell whose emf is to be measured.

(d) increase resistance in series with the cell whose emf is to be determined.

61.AB is a wire of potentiometer with the increase in the value of resistance R, the shift in the balance point J will be

(a) towards B

(b) towards A

(c) remains constant

(d) first towards B then back towards A