Question

The mutual inductance between two coils is 0.09 H. If the current in the primary coil changes from 0 to 20 A in 0.006 s, the e.m.f. induced in the secondary coil is

• A. 120 V
• B. 200 V
• C. 180 V
• D. 300 V

Hint:

Induced e.m.f. depends on how fast current changes, not on its final value.

Answer 1

The Correct Option is D

Step 1: Formula for induced e.m.f.
\[ e = M \frac{dI}{dt} \]
Step 2: Substitute given values.
\[ M = 0.09\,\text{H}, \quad \Delta I = 20\,\text{A}, \quad \Delta t = 0.006\,\text{s} \]
Step 3: Calculate rate of change of current.
\[ \frac{dI}{dt} = \frac{20}{0.006} \approx 3333.3 \]
Step 4: Induced e.m.f.
\[ e = 0.09 \times 3333.3 \approx 300\,\text{V} \]
Step 5: Conclusion.
The induced e.m.f. is 300 V.