Question

Two coils have mutual inductance of \(1.5\,H\). If current in primary coil is suddenly raised to \(5\,A\) in one millisecond, the induced emf in the secondary coil is:

• A. \(75\,V\)
• B. \(750\,V\)
• C. \(7500\,V\)
• D. \(75000\,V\)

Hint:

For sudden changes, \( \frac{dI}{dt} = \frac{\Delta I}{\Delta t} \).

Answer 1

The Correct Option is C

Concept: Induced emf due to mutual inductance: \[ e = M \frac{dI}{dt} \]

Step 1: Given values.
\[ M = 1.5\,H, \quad \Delta I = 5\,A, \quad \Delta t = 1\,ms = 10^{-3}s \]

Step 2: Substitute values.
\[ e = 1.5 \times \frac{5}{10^{-3}} = 1.5 \times 5000 = 7500\,V \] \[ \therefore e = 7500\,V \]