The mutual inductance of two co-axial coils is 2 H. If the current in one coil changes uniformly from zero to 1.0 A in 100 ms, the emf induced in the other coil is
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → \( -20\,\mathrm{V} \)
The emf induced in one coil by a changing current in the other is given by the mutual inductance, and the negative sign is Lenz's law (the emf opposes the increase of current).
\( \displaystyle \varepsilon = -M\,\frac{dI}{dt} \)
\( M = 2\,\mathrm{H} \)
\( \Delta I = 1.0\,\mathrm{A} \)
\( \Delta t = 100\,\mathrm{ms} = 0.1\,\mathrm{s} \)
\( \displaystyle \varepsilon = -2 \times \frac{1.0}{0.1} = -20\,\mathrm{V} \)