A $4.0 - \mathrm { mH }$ coil carries a current of $5.0 \mathrm {~A}$. How much energy is stored in its magnetic field?
A) $20 \mathrm {~mJ}$
B) $2.0 \mathrm {~mJ}$
C) $10 \mathrm {~mJ}$
D) none of the given answers

Question

Quizplus · Accepted Answer

The energy stored in the magnetic field of a coil (inductor) is given by the formula $E = \frac{1}{2} L I^2$, where $E$ is the energy in joules, $L$ is the inductance in henries, and $I$ is the current in amperes. Substituting the given values, $E = \frac{1}{2} \times 4.0 \times 10^{-3} \times (5.0)^2 = 0.05 \, \text{J}$ or $50 \, \text{mJ}$, which is not among the given options.

A 4.0−mH4.0 - \mathrm { mH }4.0−mH Coil Carries a Current Of

A $4.0 - \mathrm { mH }$ Coil Carries a Current Of