An inductor coil stores 64   J of magnetic field energy and dissipates energy at the rate of 640  …

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).
 
  1. 0.4
  2. 0.2
  3. 0.125
  4. 0.8

Solution

Energy stored in an inductor, U=12LI2
⇒64=12L(8)2 ⇒L=2 H
and power dissipated in a resistor, P=I2R
⇒640=(8)2R ⇒R=10 Ω
Time constant of the LR DC circuit is,
τ=LR=210=0.2 s

Asked in: JEE Main 2021 (26 Aug Shift 1)

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