Question

A coil having a resistance of 20 ohm and inductance 20 henry is connected to 120 V battery. Find the value of energy stored in the magnetic field when the steady state is reached

• A. 250 J
• B. 150 J
• C. 300 J
• D. 360 J

Answer 1

Answer: (D)

360 J

Answer 2

Here, R = 20$\Omega$, L = 20 H and E = 120 V $\therefore$ $I_0 = \frac{E}{R} = \frac{120}{20}$ = 6A Energy stored = $\frac{1}{2} LI_0\, ^2 = \frac{1}{2} \times 20 \times 36$ = 360 J