The e.m.f. induced in a secondary coil is `20000 V` when the current breaks in the primary coil. The mutual inductance is `5H` and the current reaches to zero in `10^(-4) sec` in the primary. The maximu current in the primary before it breaks is

Options

A. `0.1 A`
B. `0.4A`
C. `0. 6A`
D. `0.8 A`

Answer

B

Explanation

`e = -M.((i_(2)-i_(1)))/("time") , 2 xx 10^(4) = (-5(0-i_(1)))/(10^(-4))`
`Mi = (4 mu_(0) xx l^(2) i)/(pi L sqrt(2))`