A conducting circular loop is placed in a uniform magnetic field, `B=0.025T` with its plane perpendicular to the loop. The radius of the loop is made to shrink at a constant rate of `1 mms^(-1)`. The induced emf when the radius is `2 cm` is

Options

A. `2muV`
B. `2pimuV`
C. `pimuV`
D. `pi/2muV`

Answer

C

Explanation

`varphi=B(pir^(2))rArre=(dvarphi)/dt=B(2pir)(dr)/dt`
`rArre=0.025xx2pixx2xx10^(-2)xx10^(-3)`
= `pimuV`.