Energy stored in an inductor, U=21LI2
⇒64=21L(8)2⇒L=2H
and power dissipated in a resistor, P=I2R
⇒640=(8)2R⇒R=10Ω
Time constant of the LRDC circuit is,
τ=RL=102=0.2s
JEE Main 2021 — Physics Electromagnetism
An inductor coil stores 64J of magnetic field energy and dissipates energy at the rate of 640W when a current of 8A is passed through it. If this coil is joined across an ideal battery, find the time constant of the circuit (in s).
Held on 26 Aug 2021 · Verified 6 Jul 2026.
0.4
0.2
0.125
0.8
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