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An inductor coil stores 64 J of magnetic field energy and dissipates energy at the rate of 640 W 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 seconds:
- (1) 0.4
- (2) 0.8
- (3) 0.125
- (4) 0.2
Correct answer: (4) 0.2
Solution
The time constant of an RL circuit is given by the formula τ = (L)/(R). Here, the energy stored in the inductor and the power dissipated can be used to find the inductance and resistance, leading to a time constant of 0.2 seconds.
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