A thin circular ring of area A is held perpendicular to a uniform field of induction B. A

small cut is made in the ring and a galvanometer is connected across the ends such that

the total resistance of the circuit is R. When the ring is suddenly squeezed to zero area,

the charge flowing through the galvanometer is

Lenz’s law applies to

A coil having 500 square loops of side 10 cm is placed normal to magnetic flux which

increases at a rate of 1 T/s. The induced e.m.f. is ( )

(a) (b) (c) (d)

A conducting circular loop is placed in a uniform magnetic field of induction B tesla with

its plane normal to the field. Now, the radius of the loop starts shrinking at the rate

*dr/dt+. Then the induced e.m.f. at the instant when the radius is ‘r’, is ( )

(a) (b) (c) (d) 2r[dr/dt]

A square loop of wire of each side 50 cm is kept, so that its plane makes an angle ‘ $\theta$  ’ with a uniform magnetic field of induction 1T. The magnetic field is withdrawn in 0.1
sec., It is found that the induced e.m.f. across the loop is 125mV. The angle ‘ $\theta$  ’ is

A magnetic field 2  102 T acts at right angles to a coil of area 100 cm2 with 50 turns.

The average e.m.f. induced in the coil is 0.1V, when it is removed from the field in

time‘t’. The value of ‘t’ is

(a) (b) , (c) (d)

metal disc of radius R rotates with an angular velocity ω about an axis perpendicular to its plane passing through its centre in a magnetic field of induction B acting perpendicular to the plane of the disc. The induced e.m.f. between the rim and axis of the disc is: (A) (B) (C) (D)

An emf is produced in a coil, which is not connected to an external voltage source. This cannot be due to

A circular coil expands radially in a region of magnetic field and no electromotive force is produced in the coil. This can be because a) (b) (c) (d)