An emf of 0.5 V is developed in the secondary coil, when current in primary coil changes from 5.0 A to 2.0 A in 300 milliseconds. The mutual inductance of two coils would be:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 0.05 H
Mutual inductance \( M \) is the emf induced in the secondary coil per unit rate of change of current in the primary coil.
\( \displaystyle |\varepsilon_{2}| = M\,\left|\frac{dI_{1}}{dt}\right| \;\Rightarrow\; M = \frac{|\varepsilon_{2}|}{|dI_{1}/dt|} \)
\( \Delta I_{1} = 5.0 - 2.0 = 3.0\,\mathrm{A} \)
\( \Delta t = 300\,\mathrm{ms} = 0.3\,\mathrm{s} \)
\( \displaystyle \left|\frac{dI_{1}}{dt}\right| = \frac{3.0\,\mathrm{A}}{0.3\,\mathrm{s}} = 10\,\mathrm{A\,s^{-1}} \)
\( \displaystyle M = \frac{0.5\,\mathrm{V}}{10\,\mathrm{A\,s^{-1}}} = 0.05\,\mathrm{H} \)
Note: A similar question was also asked in CUET (UG) 2026 on 30-05-2026 (Slot 2).