Question

An emf of 91 mV is induced in the windings of a coil, when the current in a nearby coil is increasing at the rate of 1.3 A/s, what is the mutual inductance (M) of the two coils in mH?

Hint:

Mutual inductance relates induced emf to rate of current change; \( M = \frac{\epsilon}{\frac{dI}{dt}} \).

Answer 1

Induced emf due to mutual inductance:
\[ \epsilon = M \frac{dI}{dt}. \] Given: \( \epsilon = 91 \, \text{mV} = 0.091 \, \text{V} \), \( \frac{dI}{dt} = 1.3 \, \text{A/s} \).
\[ M = \frac{\epsilon}{\frac{dI}{dt}} = \frac{0.091}{1.3} \approx 0.07 \, \text{H} = 70 \, \text{mH}. \] Answer: 70 mH.