For the circuit shown, initially `'S'` is closed for a long time so that steady has been reached. Then at `t = 0`, `'S'` is opened, due to which the current decays to zero. The heat generated in inductor is.

Options

A. zero
B. `(E^(2)L)/(2(R+r))`
C. `(E^(2)L)/(2r(R+r))`
D. `(E^(2)R)/(2r(R+r))`

Explanation

Energy stored in inductor
`U = (1)/(2)Li_(0)^(2), i_(0) = (E)/(r ), U = (1)/(2)L(E^(2))/(r^(2))`,
fraction of energy dissipated in `'r'`
`U = (1)/(2)(LE^(2))/(r^(2))(r )/(r+R), U = (LE^(2))/(2r(R+r))`