Electromagnetic Induction MCQ Quiz - Multiple Choice Questions & Answers Page 4

31. The north pole of a bar magnet is rapidly introduced into a solenoid at one end (say A). Which of the following statements correctly depicts the phenomenon taking place?

1. No induced emf is developed.
2. The end A of the solenoid behaves like a south pole.
3. The end A of the solenoid behaves like north pole.
4. The end A of the solenoid acquires positive potential.

32. A metal plate can be heated by

1. passing either a direct or alternating current through the plate.
2. placing in a time varying magnetic field.
3. placing in a space varying magnetic field, but does not vary with time.
4. both a and b are correct.

33. Identify the wrong statement.

1. Eddy currents are produced in a steady magnetic field.
2. Eddy currents can be minimized by using laminated core.
3. Induction furnace uses eddy current to produce heat.
4. Eddy current can be used to produce braking force in moving trains.

34. If number of turns in primary and secondary coils is increased to two times each, the mutual inductance

1. becomes 4 times
2. becomes 2 times
3. becomes A times
4. remains unchanged

35. When the rate of change of current is unity, the induced emf is equal to

1. thickness of coil
2. number of turns in coil
3. coefficient of self inductance
4. total flux linked with coil

36. Two inductors of inductance .L each are connected in series with opposite? magnetic fluxes. The resultant inductance is (Ignore mutual inductance)

1. zero
2. L
3. 2L
4. 3L

37. An e.m.f is produced in a coil, which is not connected to an external voltage source. This is not due to

1. the coil being in a time varying magnetic field.
2. the coil moving in a time varying magnetic field.
3. the coil moving in a constant magnetic field.
4. the coil is stationary in external spatially varying magnetic field, which does not change with time.

38. Eddy currents do not cause

1. damping
2. heating
3. sparking
4. loss of energy

39. A wire loop is rotated in a magnetic field such that the frequency of change of direction of the induced emf is

1. Six times per revolution
2. Four times per revolution
3. Twice per revolution
4. Once per revolution

40. Which of the following is the equivalent quantity of mass in electricity?

1. Current
2. Charge
3. Potential
4. Inductance