Electromagnetic Induction · Question 29

A conducting circular loop is placed in a uniform magnetic field, B = 0.025 T with its plane perpendicular to the field. The radius of the loop is made to shrink at a constant rate of 1 mm s-1. The induced emf when the radius is 2 cm, is

1. 2
3. 2
4. 2

A rectangular, a square, a circular and an elliptical loop, all in the (x-y) plane, are moving out of a uniform magnetic field with a constant velocity V = v i. The magnetic field is directed along the negative z axis direction. The induced emf, during the passage of these loops, out of the field region, will not remain constant for

1. the circular and the elliptical loops
2. only the elliptical loop
3. any of the four loops
4. the rectangular, circular and elliptical loops

A conducting circular loop is placed in a uniform magnetic field 0.04 T with its plane perpendicular to the magnetic field. The radius of the loop starts shrinking at 2 mm/s. The induced emf in the loop when the radius is 2 cm is

1. 4.8 V
2. 0.8 V
3. 1.6 V
4. 3.2 V

A long solenoid has 500 turns. When a current of 2 ampere is passed through it, the resulting magnetic flux linked with each turn of the solenoid is 4 10-3 Wb. The self-inductance of the solenoid is

1. 1.0 henry
2. 4.0 henry
3. 2.5 henry
4. 2.0 henry

A circular disc of radius 0.2 meter is placed in a uniform magnetic field of induction 1 ( Wbm2 ) in such a way that its axis makes an angle of 60 with B. The magnetic flux linked with the disc is

1. 0.08 Wb
2. 0.01 Wb
3. 0.02 Wb
4. 0.06 Wb

Two coils of self inductance 2 mH and 8 mH are placed so close together that the effective flux in one coil is completely linked with the other. The mutual inductance between these coils is

1. 16 mH
2. 10 mH
3. 6 mH
4. 4 mH

As a result of change in the magnetic flux linked to the closed loop as shown in the figure, an e.m.f. V volt is induced in the loop. The work done (joule) in taking a charge Q coulomb once along the loop is [figure]

1. QV
2. 2QV
3. QV/2
4. zero

A coil of 40 henry inductance is connected in series with a resistance of 8 ohm and the combination is joined to the terminals of a 2 volt battery. The time constant of the circuit is

1. 5 seconds
2. 1/5 seconds
3. 40 seconds
4. 20 seconds

The magnetic flux through a circuit of resistance R changes by an amount in a time t. Then the total quantity of electric charge Q that passes any point in the circuit during the time t is represented by

1. Q = 1R t
2. Q = R
3. Q = t
4. Q = R t

For a coil having L = 2 mH, current flow through it is I = t2e-t then, the time at which emf becomes zero

1. 2 sec
2. 1 sec
3. 4 sec
4. 3 sec