Question

In a coil, the current changes form –2 A to +2A in 0.2 s and induces an emf of 0.1 V. The self-inductance of the coil is :

• A. 5 mH
• B. 1 mH
• C. 2.5 mH
• D. 4 mH

Answer 1

The Correct Option is A

The induced emf in a coil is given by:\[(\text{Emf})_{\text{induced}} = -L \frac{di}{dt}\]
In terms of magnitude:
\[|\text{Emf}_{\text{induced}}| = \left| L \frac{di}{dt} \right|\]
Given:
\[|\text{Emf}_{\text{induced}}| = 0.1 \, \text{V}\]
\[\frac{di}{dt} = \frac{2 - (-2)}{0.2} = \frac{4}{0.2} = 20 \, \text{A/s}\]
Now, solve for \( L \):
\[0.1 = L \times 20\]
\[L = \frac{0.1}{20} = 0.005 \, \text{H} = 5 \, \text{mH}\]