Electromagnetic Induction

A coil is placed perpendicular to a magnetic field of 5000 T. When the field is changed to 3000 T in 2 s, an induced emf of 22 V is produced in the coil. If the diameter of the coil is 0.02 m, then the number of turns in the coil is:

1. 35
2. 70
3. 7
4. 140

A small square loop of wire of side l is placed inside a large square loop of wire of side L (L=l2 ). The loops are coplanar and their centers coincide. The value of the mutual inductance of the system is x 10-7 H, where x= .

The magnetic flux (in weber) linked with a closed circuit of resistance 8 varies with time (in seconds) as =5t2-36t+1. The induced current in the circuit at t=2 s is A.

A ceiling fan having 3 blades of length 80 cm each is rotating with an angular velocity of 1200 rpm. The magnetic field of earth in that region is 0.5 G and angle of dip is 30 . The emf induced across the blades is N 10-5 V. The value of N is .

A square loop of side 10 cm and resistance 0.7 is placed vertically in east-west plane. A uniform magnetic field of 0.20 T is set up across the plane in north east direction. The magnetic field is decreased to zero in 1 s at a steady rate. Then, magnitude of induced emf is x 10-3 V. The value of x is .

A horizontal straight wire 5 m long extending from east to west is falling freely at right angle to horizontal component of earth's magnetic field 0.60 10-4 Wbm-2. The instantaneous value of emf induced in the wire when its velocity is 10 ms-1 is 10-3 V.

A rectangular loop of length 2.5 m and width 2 m is placed at 60 to a magnetic field of 4 T. The loop is removed from the field in 10 sec. The average emf induced in the loop during this time is

1. -2 V
2. +2 V
3. +1 V
4. -1 V

Two coils have mutual inductance 0.002 H. The current changes in the first coil according to the relation i = i0 , where i0 = 5 A and = 50 rad/s. The maximum value of emf in the second coil is V. The value of is .