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. `2pi mu V`
B. `pimuV`
C. `(pi)/2 mu V`
D. `2muV`

Answer

B

Explanation

Magnetic flux `phi=B.A =B pi r^(2)`
`EMF |e| =(dphi)/(dt)=Bpi2r (dr)/(dt) =pimuV`