# The magnetic potential energy stored in a certain inductor is 25 mJ , when current in the inductor is 60 mA…

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

(a) 1.389 H

(b) 13.89 H

(a) 138.88 H

(a) 0.138 H

Ans: (b)

Sol: Magnetic Potential Energy

$\displaystyle U = \frac{1}{2}L I^2$

$\displaystyle L = \frac{2 U}{I^2}$

$\displaystyle L = \frac{2 \times 25 \times 10^{-3}}{60 \times 60 \times 10^{-6}}$

L = 13.89 H