Question

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 seconds ______.

Options

• 0.4

• 0.8

• 0.125

• 0.2

Answer 1

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 seconds 0.2.

Explanation:

Time constant, τ = `L/R?`

Here, energy is stored in the inductor, E = `1/2LI^2`

Power, P = I²R

So, `E/P = (1/2I^2L)/(I^2R)`

= `1/2 L/R = tau/2`

⇒ `tau = (2 xx E)/P`

= `(2 xx 64)/640` (Here, E = 64J and P = 540W)

= `2/10`

= 0.2s