Electromagnetic Induction Mock Test

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Quiz: Electromagnetic Induction – Progressive Test
Total questions: 485
Questions in this round: 50
Time allotted: 70 minutes
Pass score: 60%
Total rounds: 10
Current round: 1^st
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Quiz: Electromagnetic Induction – Certificate Challenge
Total questions: 485
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Electromagnetic Induction – Progressive Test

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1 / 50

1. 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

2 / 50

2. A loop lies in the plane of the page. The magnetic field through it is out of the page and decreasing. The induced current is

a) zero because flux is decreasing

b) clockwise for half the loop and anticlockwise for the other half

c) clockwise

d) anticlockwise

3 / 50

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

a) chemical separation in an electrolyte only

b) electromagnetic induction

c) electrostatic charging by rubbing

d) heat expansion of a gas

4 / 50

4. 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

5 / 50

5. The same bar magnet is moved toward the same coil in two trials. In Trial P it is moved slowly, and in Trial Q it is moved quickly through the same displacement. The larger galvanometer deflection is expected in

a) neither trial, because a moving magnet cannot induce current

b) Trial P, because slow motion gives more time for current to settle

c) both trials, because speed has no effect on induction

d) Trial Q, because the rate of change of flux is larger

6 / 50

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

a) eddy current loss

b) resistance of air

c) gravitational loss

d) electrostatic shielding

7 / 50

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

a) unchanged

b) four times larger

c) twice the original value

d) half the original value

8 / 50

8. The dimensional formula of self-inductance can be obtained from . If , then is

9 / 50

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

From to , current rises linearly from to . From to , current remains constant. The self-inductance of the coil is constant.

During which interval is the self-induced emf zero?

a) to

b) From to

c) During the rising interval only

d) During both intervals equally non-zero

10 / 50

10. Magnetic flux linked with a single-turn loop changes uniformly from to in . The magnitude of average induced emf is

11 / 50

11. A compact way to state the magnitude part of Faraday's law is that induced emf depends on

a) the absolute resistance of empty space

b) the colour of the magnetic field lines

c) the total length of the circuit name

d) the rate at which flux linkage changes

12 / 50

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

a) ignoring the sign of all portions of the graph

b) taking only the final value of emf

c) multiplying the maximum emf by the total time interval in every case

d) dividing the signed area under the graph by the total time interval

13 / 50

13. A coil has turns, and each turn links a magnetic flux of . The flux linkage of the coil is

14 / 50

14. Eddy current heating is useful in an induction furnace because

a) eddy currents remove all resistance from the metal

b) magnetic flux must remain constant for heating

c) induced currents heat the metal

d) the metal is heated only by gravitational work

15 / 50

15. Read the short situation below.

A rectangular loop is in a uniform magnetic field. First, its plane is perpendicular to the field. Then it is slowly turned until its plane becomes parallel to the field. The magnitude of and the area of the loop remain unchanged.

What happens to the magnetic flux during this turning?

a) It remains fixed at

b) It decreases from to

c) It increases from to

d) It remains fixed at

16 / 50

16. Match the basic symbols with their usual meanings.

Column I	Column II
P.	1. Resistance
Q.	2. Current
R.	3. Magnetic flux
S.	4. Emf

a) P-3, Q-1, R-4, S-2

b) P-2, Q-4, R-1, S-3

c) P-1, Q-2, R-4, S-3

d) P-2, Q-1, R-4, S-3

17 / 50

17. A north pole of a magnet is moved away from the near face of a closed coil. The near face of the coil behaves as

a) a north pole to repel the receding magnet

b) a north pole because the magnet is north

c) no pole because the magnet is moving

d) a south pole opposing the flux decrease

18 / 50

18. A magnetic flux of changes uniformly to in . Ignoring the sign, the average induced emf for one turn is

19 / 50

19. 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

a) remains maximum throughout

b) decreases from maximum to zero

c) increases from zero to maximum

d) remains zero throughout

20 / 50

20. A secondary coil links of flux per turn when the primary current is . If the secondary has turns, the mutual inductance is

21 / 50

21. 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

a) proportional to the value of itself

b) negative and constant

c) positive and increasing

d) zero

22 / 50

22. Study the table for a uniformly rotating coil.

Row	Position of coil	Flux	Induced emf
P	Area vector parallel to	Maximum magnitude	Zero
Q	Area vector perpendicular to	Maximum magnitude	Maximum magnitude
R	Plane of coil parallel to	Maximum magnitude	Zero
S	Flux is maximum	Zero	Maximum magnitude

The row that correctly describes the rotating coil is

a) Row R

b) Row S

c) Row P

d) Row Q

23 / 50

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

24 / 50

24. 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

a) the area of the second coil must become larger

b) primary current changes its magnetic field

c) the second coil must rotate automatically

d) steady resistance in the second coil creates magnetic flux by itself

25 / 50

25. A coil has turns, but only half of the turns link a flux ; the remaining half link negligible flux. The total flux linkage is

26 / 50

26. 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 .

a) Both Assertion and Reason are true, but Reason does not explain Assertion

b) Assertion is false, but Reason is true

c) Both Assertion and Reason are true, and Reason explains Assertion

d) Assertion is true, but Reason is false

27 / 50

27. A magnetic field out of the page through a conducting loop is increasing. The induced current direction is

a) anticlockwise, because it must strengthen the increasing flux

b) clockwise, because it must produce field into the page

c) zero, because the field is perpendicular to the page

d) clockwise only if the circuit is open

28 / 50

28. A rectangular surface of area is placed in a magnetic field of . The magnetic flux through it is . The angle between and is

29 / 50

29. A north pole of a bar magnet approaches the near face of a closed coil along the coil axis. To oppose the approach, the near face of the coil should behave as

a) a north pole

b) a neutral face with no magnetic effect

c) a south pole

d) an electric positive plate

30 / 50

30. Assertion: Magnetic flux through a surface can be zero even when the magnetic field is not zero.
Reason: Flux depends on the component of along the area vector .

a) Assertion is false, but Reason is true

b) Both Assertion and Reason are true, but Reason does not explain Assertion

c) Both Assertion and Reason are true, and Reason explains Assertion

d) Assertion is true, but Reason is false

31 / 50

31. A flat coil is turned from a position where its area vector is parallel to to a position where its area vector is perpendicular to . The magnetic flux through the coil

a) changes from to

b) changes from to

c) remains zero throughout

d) remains equal to throughout

32 / 50

32. Mutual induction occurs when

a) steady current in one coil produces no magnetic field

b) changing current in one coil induces emf in a nearby coil

c) two coils must physically touch for any magnetic effect

d) resistance in one coil becomes equal to magnetic flux

33 / 50

33. Increasing the number of turns of a coil usually increases its self-inductance because

a) the current becomes zero automatically

b) resistance and inductance become the same quantity

c) field production and flux linkage both increase

d) the coil stops producing magnetic flux

34 / 50

34. Consider the statements about magnetic energy in an inductor.
I. Stored energy is proportional to when current is fixed.
II. Stored energy is proportional to when is fixed.
III. Stored energy is proportional to when is fixed.

a) I and II only

b) II and III only

c) I, II, and III

d) I only

35 / 50

35. 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.

a) I and II only

b) I only

c) I, II, and III

d) II and III only

36 / 50

36. A transformer core is laminated mainly to reduce

a) mutual induction completely

b) eddy current heating

c) the number of turns in the primary to zero

d) alternating flux in the core

37 / 50

37. The data for three sliding-rod circuits are shown below. Each rod moves perpendicular to the magnetic field.

Case
P
Q
R

The induced current magnitudes are

38 / 50

38. A coil has turns. The signed area under its induced emf-time graph is . If each turn has the same flux change, the change in flux per turn is

39 / 50

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

a) maximum negative only

b) impossible to relate to flux linkage

c) zero and increasing positively

d) maximum positive flux linkage

40 / 50

40. 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

a) zero because the field is uniform

b) along the direction of motion only

c) anticlockwise

d) clockwise

41 / 50

41. A unit record for the basic quantities in induction contains one mismatched entry. Identify the mismatched entry.

Row	Quantity	Usual SI unit
P	Magnetic field
Q	Area
R	Emf
S	Resistance

a) Row P

b) Row R

c) Row Q

d) Row S

42 / 50

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

a) opposes the flux change that produces it

b) always increases the magnetic flux without limit

c) is independent of the cause of induction

d) always opposes the original magnetic field itself

43 / 50

43. A coil experiences the same rate of flux change in two trials. In Trial P, its resistance is ; in Trial Q, its resistance is . If the induced emf is the same in both trials, the current in Trial Q is

a) half the current in Trial P

b) twice the current in Trial P

c) four times the current in Trial P

d) equal to zero only because resistance is larger

44 / 50

44. For a single-turn loop, an - graph is a rectangle: from to . The change in magnetic flux during this interval is

45 / 50

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

46 / 50

46. Study the device comparison table.

Row	Device	Main induction feature
P	Transformer	Mutual induction between windings
Q	generator	Changing flux due to rotation
R	Eddy-current brake	Induced currents oppose motion
S	Steady coil pair after switching	Continuous secondary emf with no flux change

The row that conflicts with electromagnetic induction is

a) Row P

b) Row R

c) Row S

d) Row Q

47 / 50

47. A magnetic core used for strong coupling between coils is laminated and made from soft magnetic material. These two design choices mainly reduce

a) the number of turns and area vector respectively

b) gravitational loss and chemical loss respectively

c) eddy current loss and hysteresis loss respectively

d) magnetic flux linkage and mutual induction respectively

48 / 50

48. A rod is pulled at constant speed through a magnetic field while completing a circuit. Increasing the circuit resistance while keeping , , and unchanged makes the required pulling force

a) smaller

b) larger

c) unchanged

d) infinite

49 / 50

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

a) becomes half

b) becomes zero

c) unchanged

d) doubles

50 / 50

50. A - graph for a fixed single-turn loop is a straight line with positive slope. The loop area is , and its area vector is parallel to . The induced emf is

a) increasing quadratically

b) zero because is not constant

c) negative and constant

d) positive and constant

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Electromagnetic Induction Mock Test – Class 12 Physics

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