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. Two single-turn loops undergo the flux changes shown below.

Loop	Flux change	Time taken
P
Q

The ratio of average emf magnitudes is

2 / 50

2. 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

3 / 50

3. Assertion: If an induced current helped the flux change that produced it, conservation of energy would be violated.
Reason: The induced effect would strengthen its own cause without requiring an external energy supply.

a) Assertion is false, but Reason is true

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

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

d) Assertion is true, but Reason is false

4 / 50

4. For a rotating -turn coil in a uniform magnetic field, the magnetic flux linkage is commonly written as

5 / 50

5. A sliding rod circuit has , , , and . The external force required to keep the rod moving at constant speed is

6 / 50

6. In a simple generator, brushes are used because

a) brushes make the coil area change automatically

b) maintain contact with the rotating coil

c) brushes create the magnetic field without magnets

d) brushes stop electromagnetic induction

7 / 50

7. The primary current in a coil is increased from to in two different trials. In Trial P, the change takes ; in Trial Q, the same change takes . The induced effect in a nearby secondary coil is larger in

a) both trials equally, because the final current is

b) Trial P, because the change lasts longer

c) Trial Q, because the primary current changes more rapidly

d) neither trial, because only steady current can induce emf

8 / 50

8. A long solenoid has its number of turns doubled while , , and are unchanged. Its self-inductance becomes

a) four times larger

b) unchanged

c) twice the original value

d) half the original value

9 / 50

9. Read the situation below.

A conducting loop lies flat on a table. A magnetic field through it is directed vertically downward into the table and is increasing uniformly. The loop is closed.

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

a) No current because the loop is horizontal

b) Anticlockwise

c) Clockwise

d) Alternating direction at every point of the loop

10 / 50

10. Assertion: Increasing the number of turns in a generator coil increases its peak emf if , , and remain unchanged.
Reason: The peak emf is proportional to the flux linkage change rate, and flux linkage contains the factor .

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

b) Assertion is true, but Reason is false

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

d) Assertion is false, but Reason is true

11 / 50

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

Row	Statement about
P	measures flux linkage per unit current
Q	controls the emf produced for a given
R	has SI unit
S	is the same physical quantity as resistance

The faulty statement is

a) Row S

b) Row R

c) Row Q

d) Row P

12 / 50

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

13 / 50

13. Use the graph description below.

For a rotating coil, the magnetic flux linkage graph is a cosine curve starting from its positive maximum at .

The induced emf graph begins from

a) a constant non-zero value for all

b) positive maximum at

c) zero, then positive for small

d) negative maximum at

14 / 50

14. 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.

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

15 / 50

15. 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

16 / 50

16. 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

a) copper has no magnetic flux through it

b) copper supports circulating induced currents

c) plastic changes magnetic field into gravitational field

d) plastic has larger eddy currents than copper

17 / 50

17. The coefficient of self-inductance of a coil is defined through the relation

18 / 50

18. A single-turn loop has an emf-time graph shaped like a triangle above the time axis. The base is , and the peak emf is . The corresponding flux change is

19 / 50

19. Read the case below.

A bar magnet moves along the axis of a closed coil. When its north pole approaches the coil, the galvanometer deflects to the right. The same north pole is then moved away from the coil along the same line.

What should happen to the galvanometer deflection during the second motion?

a) It should deflect to the left

b) It should again deflect to the right with the same direction

c) It should remain permanently deflected to the right

d) It should show no deflection because the same pole is used

20 / 50

20. A pair of nearby coils is adjusted so that more magnetic flux produced by the primary links the secondary. The quantity that most directly increases is

a) gravitational acceleration

b) mutual inductance

c) resistance of empty space

d) focal length of the secondary coil

21 / 50

21. In a two-coil induction setup, the coil connected to a battery and key is usually called the primary coil, while the coil connected to a galvanometer is called the secondary coil. The galvanometer deflects when

a) the secondary coil is disconnected from the galvanometer

b) the primary current is perfectly steady

c) the primary current is changing

d) the battery label is changed without changing current

22 / 50

22. Use the graph description below.

For a single-turn loop, magnetic flux increases linearly from to during the interval to .

The average induced emf during this interval is

23 / 50

23. 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

24 / 50

24. 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

25 / 50

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

b) and

c) and

d) and

26 / 50

26. For a single loop in a uniform magnetic field perpendicular to its plane, and . The magnitude of induced emf is

27 / 50

27. A hand-driven generator produces electrical output when its coil is rotated in a magnetic field. This device is based mainly on

a) direct conversion of resistance into emf

b) electromagnetic induction

c) heating of a resistor by steady current

d) production of emf by steady flux alone

28 / 50

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

29 / 50

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

d) zero

30 / 50

30. 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 only

b) I, II, and III

c) II and III only

d) I and II only

31 / 50

31. A simple generator has flux linkage . The generated emf is positive just after because

a) positive flux linkage starts decreasing

b) Faraday's law does not apply to generators

c) the coil has no magnetic field at

d) the flux linkage is zero at

32 / 50

32. Consider these statements about mutual induction.
I. It requires changing current in one coil to produce a continuing induced emf in the other.
II. Better magnetic coupling usually increases .
III. Mutual inductance is measured in .

a) I and II only

b) I only

c) I, II, and III

d) II and III only

33 / 50

33. The angle used while discussing magnetic flux through a plane surface is normally taken between

a) and the area vector

b) and the plane of the surface

c) current and resistance

d) emf and current

34 / 50

34. Assertion: A conducting rod moving in a magnetic field may have motional emf even when no closed circuit current flows.
Reason: Magnetic force can separate charges in the rod, but continuous current needs a complete conducting path.

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

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

c) Assertion is true, but Reason is false

d) Assertion is false, but Reason is true

35 / 50

35. A conducting rod of length moves with velocity in a uniform magnetic field . The rod, velocity, and field are mutually perpendicular. The higher potential end is decided by

a) the end closer to the battery, even when no battery is present

b) the direction of for positive charges

c) the direction opposite to current in every circuit

d) the direction of for positive charges

36 / 50

36. A fixed -turn coil of area is placed with its area vector parallel to a magnetic field. The field increases uniformly at , and the coil resistance is . The induced current magnitude is

37 / 50

37. 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

38 / 50

38. 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

39 / 50

39. A current through an inductor is steady for a long time in an ideal circuit. The self-induced emf is then

a) equal to

b) equal to the resistance of the wire

c) maximum because current is non-zero

d) zero because

40 / 50

40. 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) Both Assertion and Reason are true, and Reason explains Assertion

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

c) Assertion is true, but Reason is false

d) Assertion is false, but Reason is true

41 / 50

41. The peak flux linkage of a rotating coil is , and its angular speed is . The peak induced emf is

42 / 50

42. A coil is wound on a soft iron core instead of an air core. Its self-inductance usually increases mainly because

a) the core reduces flux for the same current

b) the number of turns effectively decreases

c) higher core permeability

d) the coil area becomes irrelevant

43 / 50

43. The phrase induced emf is best understood as

a) the current produced by a chemical source

b) force on charges without flux change

c) emf due to changing magnetic flux

d) resistance produced by a changing field

44 / 50

44. A closed conducting loop and an open conducting loop are placed in identical changing magnetic flux conditions. The key difference is that

a) the open loop must always have larger current

b) the closed loop cannot have changing magnetic flux

c) emf in both; current only in the closed loop

d) only the open loop can have induced emf

45 / 50

45. Eddy currents are best described as

a) circulating induced currents in bulk conductors

b) currents present without flux change

c) currents confined to insulators in steady fields

d) steady currents supplied by a cell in a wire

46 / 50

46. A statement says, “The induced current always produces a magnetic field opposite to the applied magnetic field.” The best correction is

a) the induced current direction is decided only by resistance

b) the induced current always supports any increase in magnetic flux

c) opposition is to flux change, not field itself

d) the induced magnetic field is always zero in a closed loop

47 / 50

47. A current-time graph for the primary coil is described below.

From to , the primary current rises uniformly from to . From to , it remains constant at . From to , it falls uniformly to .

During which interval is the induced emf in the secondary expected to be zero?

a) During both rising and falling intervals only

b) From to

c) From to

d) From to

48 / 50

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

a) neither coil can have induced emf because resistance is present

b) emf in both coils; current only in coil P

c) only coil Q has induced emf because it is open

d) both coils have the same induced current

49 / 50

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

50 / 50

50. A primary current-time graph is a straight line with positive slope. For a fixed pair of coils with mutual inductance , the induced emf in the secondary is

a) constant and negative

b) constant and positive for every sign convention

c) zero because the graph is straight

d) increasing quadratically with time

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Electromagnetic Induction Mock Test – Class 12 Physics

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