Calculate the energy stored in a coil if the coil carries a current of 20 A and inductance of the coil is 40 mH.

Correct option is C

​$$\text{To calculate the energy stored in a coil (inductor), we use the formula for energy stored in an inductor:} \\[1em]E = \frac{1}{2} L I^2 \\[1em]\text{Where:} \\\bullet \quad E \text{ is the energy stored in the coil,} \\\bullet \quad L \text{ is the inductance of the coil,} \\\bullet \quad I \text{ is the current flowing through the coil.} \\[1em]\text{Given:} \\\bullet \quad I = 20\,\text{A (current)} \\\bullet \quad L = 40\,\text{mH} = 40 \times 10^{-3}\,\text{H (inductance)} \\[1em]\text{First, convert the inductance from millihenries (mH) to henries (H):} \\[1em]L = 40 \times 10^{-3}\,\text{H} = 0.04\,\text{H}$$​

$$\text{Now, substitute the values into the energy formula:} \\[1em]E = \frac{1}{2} \times 0.04 \times (20)^2 \\[1em]\text{Calculate } (20)^2 : \\(20)^2 = 400 \\[1em]\text{Now, multiply:} \\E = \frac{1}{2} \times 0.04 \times 400 \\E = 0.02 \times 400 \\E = 8 \, \text{joules (J)}$$​​