Q 12-06-111JEE MainJEE Main 2021 (26 Aug, Shift 1)Easy
An inductor coil stores $64$ J of magnetic field energy and dissipates energy at the rate of $640$ W when a current of $8$ A is passed through it. If this coil is joined across an ideal battery, find the time constant of the circuit (in s).
Answer: (B) $0.2$
$\frac{1}{2}LI^2 = 64 \Rightarrow L = \dfrac{128}{64} = 2$ H.
$I^2R = 640 \Rightarrow R = \dfrac{640}{64} = 10\ \Omega$.
$\tau = \dfrac{L}{R} = 0.2$ s.
Solution by Sreeraj P, M.Sc Physics