The S.I unit of mutual inductance, the 'henry' can be written as

The correct answer is Option (2) → \( \displaystyle\frac{\text{volt-second}}{\text{ampere}} \)

The mutual inductance M of two coils is defined through the emf induced in one coil when the current in the other changes: \( |\varepsilon| = M\,\displaystyle\frac{dI}{dt} \).

    \( \displaystyle M = \frac{|\varepsilon|}{dI/dt} \)

The unit of the emf is the volt and the unit of the rate of change of current is ampere per second, so

    \( \displaystyle 1\,\mathrm{henry} = \frac{1\,\mathrm{volt}}{1\,\mathrm{ampere\,per\,second}} = \frac{\text{volt-second}}{\text{ampere}} \)