Electromagnetic Induction Mock Test – Class 12 Physics

1. In an circuit just after the switch is closed, the inductor strongly opposes the sudden rise of current. The current through the ideal inductor branch at the first instant is best described as

2. A secondary circuit of resistance carries a mutually induced current of . The electrical power dissipated as heat in the secondary resistance is

3. An inductor of inductance carries current . If the current is increased to , the increase in magnetic energy stored is

4. A - graph for a fixed coil is horizontal from to . The area vector of the coil is parallel to the field during this interval. The induced emf during this interval is

5. A fixed loop is placed in a magnetic field whose magnitude varies with time. The area vector of the loop is perpendicular to throughout. The induced emf due to this varying is zero because

6. A sliding rod is pulled faster while moving through the same magnetic field on the same rails. The external mechanical power needed increases more than linearly because

7. In a generator coil with turns rotating in a uniform magnetic field, if the peak flux through each turn is and , the peak emf is

8. A single-turn loop has an emf-time graph that is positive for the first half of an interval and negative for the second half. The positive area is larger than the negative area in magnitude. The net flux change is

9. Assertion: If magnetic flux through a closed loop increases, the induced current acts so as to oppose that increase.
Reason: The negative sign in Faraday's law represents Lenz's law.

10. In the same primary-secondary coil arrangement, the galvanometer deflection on opening the key is opposite to that on closing the key. The reversal occurs because

11. A closed loop has induced emf because its linked flux is changing. If the loop resistance is increased while the same flux-change rate is maintained, the induced current

12. A pair of coils has . The primary current changes at , and the secondary circuit resistance is . The magnitude of secondary current is

13. A conducting rod moves parallel to a uniform magnetic field. For the usual straight-rod motional emf case, the emf across the rod is

14. For a series circuit connected to a source, the current growth is governed by the time constant

15. A bar magnet is held fixed near a closed coil connected to a sensitive galvanometer. What is expected after the magnet and coil have both become stationary?

16. A magnetic field directed out of the page through a conducting loop is increasing. To oppose this change, the induced magnetic field due to the loop should be

17. The magnetic field inside a long solenoid carrying current is written as

18. For discussing electromagnetic induction in a coil, the most directly relevant prerequisite set is

19. A graph of current against time for an circuit after the source is disconnected is best described as

20. Study the device comparison table.

The row that conflicts with electromagnetic induction is

21. A long solenoid has , , , and . If its current changes at , the magnitude of self-induced emf is

22. A generator converts mechanical energy into electrical energy mainly through

23. A closed sliding-rod circuit has a constant induced current while the rod moves at constant speed in a uniform magnetic field. This constancy occurs because

24. Two coil pairs have the same primary current-change rate. Pair P has mutual inductance , while pair Q has mutual inductance . The ratio of secondary induced emf magnitudes is

25. A rod of length moves perpendicular to a magnetic field with speed . If both and are doubled while is unchanged, the motional emf becomes

26. In a nearby-coil arrangement, current in one coil is increased steadily while a second coil remains fixed near it. The magnetic flux linked with the second coil changes because

27. Two long coaxial solenoids have mutual inductance . If the primary current changes from to in , the magnitude of average emf induced in the secondary is

28. One setup has a coil and magnet at rest relative to each other. Another setup has the same magnet moving toward the same coil. The second setup is more likely to show induction because

29. The average value of induced emf over a time interval can be obtained from an - graph by

30. In a metal detector, a changing magnetic field can help identify a nearby metal object because

31. A coil experiences a flux change of in . A second trial with the same coil gives the same flux change in . Ignoring sign, the ratio of average induced emf magnitudes in the first and second trials is

32. A solenoid is filled with a material whose permeability is times that of air, while its geometry and number of turns remain unchanged. Its self-inductance becomes

33. A rod moves perpendicular to a magnetic field. The motional emf is . The speed of the rod is

34. The sign of the induced emf in mutual induction is decided by

35. In mutual induction, the coil in which current is changed is often called the primary coil, while the coil in which emf is induced is called the secondary coil. The induced emf in the secondary depends directly on

36. For a rotating coil with , , , and , the peak induced emf is

37. Consider the following statements about changing magnetic flux.
I. Flux can change even if the loop is stationary.
II. Flux can change even if the magnetic field is steady.
III. Flux can change only when the circuit resistance changes.

38. Use the graph description below.

The average induced emf during this interval is

39. A pair of coaxial solenoids has , , common area , common length , and . Their mutual inductance is

40. A long solenoid is made wider so that its cross-sectional area becomes three times larger, while , , and remain unchanged. Its self-inductance becomes

41. Two coils have the same flux through each turn. Coil P has turns and coil Q has turns. The ratio of their flux linkages is

42. A secondary coil of turns has flux through each turn changing uniformly by in . Its average induced emf magnitude is

43. For a rotating coil with flux linkage , the induced emf is

44. A pair of coils has mutual inductance . The primary current changes according to , where is in . The magnitude of secondary induced emf at is

45. A pair of coils has . The primary current is , where is in seconds. The magnitude of the secondary emf at is

46. A learner says, “An inductor opposes current.” The better statement is that an inductor

47. The current in a inductor is increased uniformly from to . The increase in stored magnetic energy is

48. A series circuit has , , and . The steady current after a long time is

49. A square loop in a steady uniform magnetic field is compressed so that its area becomes half, while its area vector remains parallel to . The new magnetic flux is

50. A coil is connected to an ideal voltmeter but not to a closed conducting circuit. The magnetic flux linked with the coil changes with time. The most suitable statement is that