Electromagnetic Induction Mock Test – Class 12 Physics

1. A series circuit has and . Its time constant is

2. A secondary coil of resistance is linked to a primary coil with . If the primary current changes uniformly at , the heat produced in the secondary in is

3. Lenz's law states that the direction of induced current is such that it

4. For a closed circuit of resistance , an induced emf produces an induced current given by

5. Read the situation below.

What is the induced current as seen from above the table?

6. Use the observations below from a magnet-coil experiment.

The row that conflicts with the usual observation is

7. A -turn coil has flux through each turn changing at a rate of . The total resistance of the closed coil circuit is . Ignoring sign, the induced current is

8. A magnet is moved toward a coil connected to a galvanometer. A deflection is observed. When the same magnet is held at rest at the same final position, the galvanometer shows no deflection because

9. 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

10. Two equal surfaces are placed in the same uniform magnetic field. Surface P has between and , while Surface Q has . The fluxes and satisfy

11. Study the table for a loop in a uniform magnetic field perpendicular to its plane.

The row that gives the correct induced current is

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

13. A rectangular loop moves to the right and begins to enter a region of uniform magnetic field directed into the page. While the loop is entering, the induced current is

14. In a simple generator arrangement, the emf induced in the rotating coil is internally alternating, but the external output becomes unidirectional because

15. Two coaxial solenoids have mutual inductance . The current in the primary changes from to according to a straight-line graph in . If the secondary has resistance , the total charge that passes through the secondary during this change is

16. The same rectangular loop is moving completely inside a large uniform magnetic field region with constant speed. Its area, orientation, and the field through it remain unchanged. The induced emf is

17. A primary coil carries a constant current after the key has been closed for a long time. A nearby secondary coil is connected to a galvanometer. The expected galvanometer response is

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

19. A coil has turns. During a time interval, the flux through each turn changes from to . The average induced emf is

20. A loop is shrinking at a constant rate in a uniform magnetic field directed out of the page. The induced current in the closed loop is

21. At the instant when the area vector of a rotating coil is parallel to , the magnetic flux through the coil is

22. Assertion: Laminated transformer cores reduce unwanted heating.
Reason: Laminations restrict large eddy-current loops inside the core.

23. The magnetic flux through a plane surface is for a chosen area vector . If the same surface is assigned the opposite area vector without changing the physical field, the flux becomes

24. A coil and a magnet are arranged so that only their relative motion changes: in Case 1 the magnet moves toward a fixed coil, and in Case 2 the coil moves toward a fixed magnet with the same relative speed. The induced effect is expected to be similar because

25. A fixed coil has area vector making with a uniform magnetic field. The field changes at a rate of . The coil has turns and area . The magnitude of induced emf is

26. A source is connected to a series circuit containing and . At the instant when the current is during growth, the magnitude of is

27. Consider the following statements about induced emf.
I. Its magnitude increases when the same flux change occurs in less time.
II. Its direction is decided by Lenz's law.
III. It can exist only after an induced current has already started flowing.

28. Consider these statements about Faraday's law for a coil.
I. The emf increases with if the flux change per turn is unchanged.
II. The negative sign gives the direction according to Lenz's law.
III. The resistance of the coil appears in .

29. 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

30. A rectangular loop has height and total resistance . It enters a uniform magnetic field of at . The field is perpendicular to the loop. During entry, the induced current magnitude is

31. Study the device comparison table.

The row that conflicts with electromagnetic induction is

32. The emf of a generator coil is described by , with peak emf . At , the flux linkage is most consistent with

33. A rectangular loop moves completely inside a large region of uniform magnetic field with constant speed. Its area, orientation, and the field through it remain unchanged. The magnetic flux linked with the loop

34. A student writes that flux must be maximum whenever the plane of the coil is parallel to the magnetic field. The better correction is that flux is maximum when

35. The slope of a - graph for a -turn coil is per turn. The induced emf is

36. A rod of length slides on rails with constant speed in a uniform magnetic field perpendicular to the rail plane. The derivation from changing flux gives the induced emf because

37. The energy-current graph for an ideal inductor of constant is

38. Read the graph case below.

The net change in magnetic flux from to is

39. In a device core, the same induced emf is produced around a possible eddy-current path. If the effective resistance of that path is made four times larger, the eddy current becomes

40. A learner uses instead of for magnetic flux. The best diagnosis of the error is that the learner has

41. A simple generator is rotated faster, but the magnetic field strength and coil dimensions are unchanged. The maximum magnetic flux through each turn

42. If the current in an inductor is doubled while remains unchanged, the stored magnetic energy becomes

43. Match the basic symbols with their usual meanings.

44. A loop in the plane of the page has a magnetic field into the page increasing uniformly. If its resistance is doubled while the same field change is maintained, the induced current direction and magnitude change as

45. In a transformer, leakage flux refers to magnetic flux that

46. Two nearby coils are arranged so that changing current in coil P induces emf in coil Q. If the same current change in P is made in half the time, the magnitude of emf in Q

47. A south pole is moved away from a closed coil. Viewed from the magnet side, the near face of the coil must become a north pole. The induced current as seen from that side is

48. 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

49. A sign convention is chosen so that positive flux is along the chosen area vector. In a single loop, changes from to in . The average induced emf is

50. Study the cases for a loop lying in the plane of the page.

The row that gives the correct induced current is