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 ).

Step-by-step solution

Energy stored in an inductor, U = 1 2 L I 2 ⇒ 64 = 1 2 L ( 8 ) 2   ⇒ L = 2   H and power dissipated in a resistor, P = I 2 R ⇒ 640 = ( 8 ) 2 R   ⇒ R = 10   Ω Time constant of the L R   D C circuit is, τ = L R = 2 10 = 0 . 2   s