A Uniform flux density of 0.1 Wb m2 extends over a plane circuit of area 1 m2, and is normal to it. How quickly must the field be reduced to zero if an emf of 100 V is to be produced?

10–2 Sec       10–3 sec   0.1Sec 1 micro sec.

10–3 sec

$\phi_1 = BA = 0.1\times 1 = 0.1 wb , \phi_2 = 0$ $t = \frac{\phi_1 - \phi_2 }{\xi} = \frac{0.1}{100} = 10^{-3}Sec$