A solenoid has `2000` turns wound over a length of `0.3 m`. Its cross-sectional area is equal to `1.2 xx 10^(-3) m^(2)`. Around its central cross-section a coil of `300` turns in wound. If an initial current of `2 A` flowing in the solenoid is reversed in `0.25 s`, the emf induced in the coil is

Options

A. `0.6 mV`
B. `60 mV`
C. `48 mV`
D. `0.48 mV`

Answer

C

Explanation

Since, `epsilon = (d phi)/(dt) = (d)/(dt) (NBA)`
`epsilon = (d)/(dt) [NA(mu_(0) nI)]`, `epsilon = NA mu_(0) n((dI)/(dt))`
where `N` is total number of turns in the coil and `n` is the number of turns per unit length in the solenoid.
`epsilon = (300) (1.2 xx 10^(-3))(4pi xx 10^(-7)) xx (2000)/(0.3) xx (4)/(0.25)`
`epsilon = 4.8 xx 10^(-2) V = 48 mV`