Physics-Electromagnetic Induction

Test Preparation on Physics - Electromagnetic Induction

1.

A coil of an area 102 cm has 200 turns. The magnetic field of 20.1 Wb/m2 is perpendicular to the coil. The field is reduced to zero in 0.1 sec, the induced emf in the coil is :

11 V
20.2 V
32 V
4zero

The induced emf in the coil is e = N df/at = N d(BA)/dt =NA(dB/dt) e = 200

2.

When current changes from 13 A to 7 A in 0.5 sec through a coil, the emf induced is 3x10-4V. The coefficient of self induction is :

125 x 10-3 H
225 x 10-4 H
325 x 10-5 H
425 x 10-6 H

Coefficient of self induction is given by e = -L di/dt \ L = e/di/dt = -300 x 10-6 x 0.5 /(7 - 1 3 ) = 25

3.

In LR circuit, the time constant is given by :

1LR
2R/L
3L/R
4l/LR

4.

In a step up transformer the number of turns in :

1primary are less
2primary are more
3primary and secondary are equal
4primary are infinite

5.

Two pure inductor coils of self inductance L each areconnected in series, the net inductance is :

1L
22L
3L/2
4L/4

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