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

Options

A. 3.2 `pimuV`
B. 4.8 `pimuV`
C. 0.8 `pimuV`
D. 1.6 `pimuV`

Answer

A

Explanation

`|e|=(dvarphi)/dt=B(dA)/dt=Bd/dt(pir^(2))`
`rArr|e|=2piBr(dr)/dt`
`rArr|e|=2pixx0.04xx2xx10^(-2)xx2xx10^(-3)`
= `3.2pixx10^(-6)V=3.2pimuV`.