Question

The coefficient of mutual induction is 2 H and induced e.m.f. across secondary is 2 kV. Current in the primary is reduced from 6 A to 3 A. The time required for the change of current is ______.

Options

• 4 × 10^-3 s

• 6 × 10^-3 s

• 2 × 10^-3 s

• 3 × 10^-3 s

Answer 1

The coefficient of mutual induction is 2 H and induced e.m.f. across secondary is 2 kV. Current in the primary is reduced from 6 A to 3 A. The time required for the change of current is 3 × 10^-3 s.

Explanation:

\[\mathbf{e}_{s}=\mathbf{M}\cdot\frac{\mathrm{dI}_{p}}{\mathrm{dt}}\]

\[\therefore\] dt = M . \[\frac {dI_p}{e_s}\]

\[\therefore\] dt = 2 × \[\frac{6-3}{2\times10^3}=3\times10^{-3}\mathrm{s}\]