MCQs of Electromagnetic Induction

Electromagnetic Induction MCQs

MCQs of Electromagnetic Induction

Showing 51 to 60 out of 113 Questions

51.

A horizontal electric pole wire 200 m long is lying along the Earth’s magnetic field at a height of 10 m. If horizontal component of the Earth’s magnetic field is 0.32 × 10^-4 T, then emf induced in the wire, on striking the ground, is _____. ( g = 9.8 )

(a)	0.25 V
(b)	0.15 V
(c)	0.09 V
(d)	0.05 V

52.

A metal rod of length L is pivoted at its upper end. It is released from a horizontal position. There is an uniform magnetic field perpendicular to its plane of rotation. When it becomes vertical, the potential across its ends is proportional to _____.

(a)	L
(b)	L²
(c)	$L^{\frac{1}{2}}$
(d)	$L^{\frac{3}{2}}$

53.

The significance of the self-inductance L is same as that of _____ in the linear motion.

(a)	mass
(b)	velocity
(c)	acceleration
(d)	displacement

54.

In 0.1 s, the current in a coil increases from 1 A to 1.5 A. If inductance of coil is 60 mH, then induced current in an external resistance of 3 Ω will be _____.

(a)	1 A
(b)	0.5 A
(c)	0.2 A
(d)	0.1 A

55.

If the number of turns of a solenoid are doubled and its length is halved keeping the area of cross-section same, then the ratio of initial and final self-inductances will be _____.

(a)	4 : 1
(b)	1 : 4
(c)	1 : 8
(d)	8 : 1

56.

An electromagnet has stored 648 J of energy, when a current of 9 A exists in its coils. If the current is reduced to 0.3 s, then the average induced emf in the coils is _____.

(a)	120 V
(b)	240 V
(c)	320 V
(d)	480 V

57.

Which of the following does not obey the phenomenon of mutual induction ?

(a)	Dynamo
(b)	Transformer
(c)	Induction coil
(d)	Electric heater

58.

The mutual inductance of two coils can be increased by _____.

(a)	increasing the length of coils
(b)	increasing the number of turns in the coils
(c)	winding the coils on wooden cores
(d)	decreasing the number of turns in the coils

59.

A wire of fixed length is wound into a solenoid of length l and radius r, its self inductance is found to be L . Now, if the same wire is wound into a solenoid of length \frac{l}{2} and radius \frac{r}{2}, then the self - inductance will be

_____.

(a)	2L
(b)	L
(c)	4L
(d)	8L

60.

An electric motor operates at 20 r.p.s. What will be the approximate power delivered by the motor, if it supplies a torque of 75 Nm?

(a)	1550 W
(b)	4040 W
(c)	7730 W
(d)	9420 W

Showing 51 to 60 out of 113 Questions