Question

The magnetic potential energy stored in a certain inductor is 25 mJ, when the current in the inductor is 60 mA. This inductor is of inductance

• A. 0.138H
• B. 1.389H
• C. 138.88H
• D. 13.89H

Answer 1

The Correct Option is D

To find the inductance of the inductor, we use the formula for magnetic potential energy:

\[ U = \frac{1}{2} L I^2 \]

Where:

• \( U \) = energy stored
• \( L \) = inductance
• \( I \) = current

Given:

• \( U = 25\,\text{mJ} = 25 \times 10^{-3}\,\text{J} \)
• \( I = 60\,\text{mA} = 60 \times 10^{-3}\,\text{A} \)

Substitute values:

\[ 25 \times 10^{-3} = \frac{1}{2} L (60 \times 10^{-3})^2 \]

Simplify:

1. \[ (60 \times 10^{-3})^2 = 3.6 \times 10^{-3} \]
2. \[ L = \frac{2 \times 25 \times 10^{-3}}{3.6 \times 10^{-3}} \]
3. \[ L = \frac{50}{3.6} \approx 13.89\,\text{H} \]

Final Answer: \( 13.89\,\text{H} \)