Electromagnetic Induction Mock Test – Class 12 Physics

1. A generator produces . Its frequency is

2. A transformer core is made of many thin insulated sheets instead of one solid iron block. This design mainly reduces

3. Two identical coils experience the same changing magnetic flux. Coil P is closed with resistance , while coil Q is open. The better comparison is

4. Lenz's law is closely connected with conservation of energy because the induced current

5. Assertion: A closed loop can have changing magnetic flux even when it is not moving.
Reason: A time-varying magnetic field can change in the relation .

6. An inductor stores of energy when it carries . Its inductance is

7. A rigid loop rotates in a uniform magnetic field while its area and the field strength remain constant. The magnetic flux through it changes because

8. For two long coaxial solenoids with common cross-sectional area , common length , and turn densities and , the standard mutual inductance is

9. A - graph for a loop is a straight line sloping downward. What can be concluded about the induced emf during that interval?

10. In an circuit, increasing while keeping fixed makes the current change more slowly because

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

12. A simple generator uses slip rings rather than a split-ring commutator because the desired output is

13. In a simple magnet-coil observation, the galvanometer deflects when the magnet is pushed toward the coil and deflects oppositely when the magnet is pulled away. What does the reversal mainly show?

14. A rod slides to the right on two conducting rails in a magnetic field directed into the page. The circuit is closed through a resistor on the left side of the rails. The induced current in the rod is

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

16. A closed coil near a moving magnet has resistance . When induced current flows, the heat produced in the coil is best traced back to

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

18. A current-time graph for a coil is described below.

During which interval is the self-induced emf zero?

19. A transformer core is laminated mainly to reduce

20. A non-conducting plastic plate and a copper plate of the same shape are moved through the same magnetic field region. Eddy-current braking is much stronger for the copper plate because

21. Read the graph case below.

The net change in magnetic flux from to is

22. A generator coil rotates from a position where its area vector is parallel to to a position where its plane is parallel to . During this quarter turn, the magnitude of flux through the coil

23. The induced emf in the secondary coil due to changing primary current is

24. A sliding rod of length moves at on conducting rails in a uniform magnetic field . The total circuit resistance is . The magnetic drag force on the rod is

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

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

27. A conducting rod moves perpendicular to a magnetic field, but its speed-time graph is a straight line through the origin. If and are constant, the motional emf-time graph is

28. A circular loop lies in the page. The external magnetic field through it changes from out of the page to out of the page while the area remains constant. The induced current is

29. A conducting loop is kept in a uniform magnetic field. Without changing the material of the loop, magnetic flux linked with it can be changed by changing

30. A fixed -turn coil of area is placed with its area vector parallel to a magnetic field. The magnetic field decreases uniformly from to in . The average induced emf is

31. Mutual inductance between two coils is increased when

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

33. The signed area under an - graph for a single-turn loop is . The flux change is

34. A magnet is pushed toward a closed coil and a repulsive magnetic effect is felt. This resistance to motion occurs because

35. For a coil of turns with the same flux linked through each turn, Faraday's law is

36. A device needs strong mutual induction between two windings but small eddy current loss in the core. The most suitable choice is

37. In the relation , the dot product shows that magnetic flux is

38. A coil has flux linkage , where is in and in . At , the effective inductance is

39. Use the arrangement described below. A rectangular coil rotates between the poles of a magnet and is connected to two slip rings. The external circuit contains a lamp.
What happens to the lamp brightness in the simplest ideal generator model?

40. An open conducting loop is moved near a magnet so that the magnetic flux linked with the loop changes. The most suitable conclusion is that

41. A table gives possible meanings of in self-induction.

The faulty statement is

42. A circular loop of area lies in the plane of the page. The magnetic field into the page increases uniformly from to in . For a single turn, the magnitude of average induced emf is

43. A rod moves at in a magnetic field. The angle between and is , and the standard oblique motional-emf geometry applies. The emf is

44. In a uniform magnetic field, a plane surface has area . The field makes an angle of with the plane of the surface, not with the area vector. The flux through the surface is

45. A metal ring is moved toward a region of stronger magnetic field, and the motion becomes harder when the ring is closed. If the ring is cut so that it is open, the resisting effect becomes much weaker. The main reason is that

46. The line resistance in a transmission system is . If the current is reduced from to by using a higher transmission voltage, the power loss changes from

47. Use the graph description below.

The induced emf-time graph should have

48. Mutual induction occurs when

49. In a mutual-induction experiment, the primary current is first increased uniformly and then decreased uniformly at the same rate. The induced emf in the secondary during the decrease is

50. In a magnet-coil experiment, the coil is connected to a galvanometer but the circuit is accidentally left open. When the magnet is moved toward the coil, the most suitable statement is that