Question

A coil having an area 2m² is placed in a magnetic field which changes from 1Wb /m² to 4Wb /m² in a interval of 2 second. The e.m.f. induced in the coil will be(a) 4 V(b) 3 V(c) 1.5 V(d) 2 V

Answer 1

answer : option (b) 3V

explanation : cross sectional area of the coil, A = 2m²

initial magnetic field, $B_i$ = 1Wb/m²

final magnetic field, $B_f$ = 4Wb/m²

time taken to change the magnetic field, t = 2sec

induced emf , $\xi_{in}=-\frac{d\phi}{dt}$

= - $A\frac{dB}{dt}$

= - 2 × (4 - 1)/2

= - 3V

hence, magnitude of induced emf in the coil will be 3V