In Fig (a) and (b), two air-cored solenoids `P` and `Q` have been shows. They are placed near each other. In Fig (a), when `I_(P)`, the current in `P`, changes at the rate of `5 A s^(-1)`, an emf of `2 mV` is induced in `Q`. The current in `P` is then switched off, and the current changing at `2 A s^(-1)` is fed through `Q` as shows in the figure. What emf will be induced in `P`?

Options

A. `8 xx 10^(-4) V`
B. `2 xx 10^(-3) V`
C. `5 xx 10^(-3) V`
D. `8 xx 10^(-2) V`

Answer

A

Explanation

For first case : `2 mV = Mxx5`
For second case : `e = M xx 2`
Solve to get `e = 0.8 mV = 8 xx 10^(-4) V`