A Pair of coils of turns `n_(1)` and `n_(2)` are kept close together. Current passing through the first is reduced at r, and emf 3 mV is developed across the other coil. If the second coil carries current which is then reduced at the rate 2 r, the emf produced across the first coil will be

Options

A. `(6 n_(1))/(n_(2)) mV`
B. `(6 n_(2))/(n_(1)) mV`
C. 6 mV
D. `3//2 mV`

Answer

C

Explanation

From `e = M ((dI)/(dt))`, we find that `e prop ((dI)/(dt))`
As `M_(12) = M_(21)`, therefore, when `(dI//dt)` is doubled, iuduced e.m.f. is also double i.e.,
`e = 2 xx 3 mV = 6 m V`