The value of inductance needed to store 4kWh of energy in a coil carrying a 2000A current is:

Correct option is B

$$\text{To solve this problem, we can use the formula for the energy stored in an inductor:} \\[6pt]E = \dfrac{1}{2} L I^2 \\[8pt]\text{Where:} \\[4pt]\bullet E = \text{the energy stored (in joules)} \\[4pt]\bullet L = \text{the inductance (in henries)} \\[4pt]\bullet I = \text{the current (in amperes)} \\[8pt]\text{First, let's convert the given energy from kilowatt-hours (kWh) to joules:} \\[4pt]1\,\text{kWh} = 3600\,\text{kJ} \\[4pt]4\,\text{kWh} = 4 \times 3600 = 14400\,\text{kJ} = 14400 \times 10^3\,\text{J} \\[8pt]\text{Now, substitute the known values into the formula:} \\[6pt]14400 \times 10^3 = \dfrac{1}{2} L (2000)^2 \\[8pt]14400 \times 10^3 = \dfrac{1}{2} L \times 4000000 \\[8pt]L = \dfrac{14400 \times 10^3 \times 2}{4000000} \\[8pt]L = \dfrac{28800 \times 10^3}{4000000} \\[8pt]L = 7.2\,H$$​​