Question

For L-R circuit, the time constant is equal to

(A) Twice the ratio of the energy stored in the magnetic field to the rate of dissipation of energy in the resistance. 

(B) Ratio of the energy stored in the magnetic field to the rate of dissipation of energy in the resistance. 

(C) Half the ratio of the energy stored in the magnetic field to the rate of dissipation of energy in the resistance. 

(D) Square of the ratio of the energy stored in the magnetic field to the rate of dissipation of energy in the resistance.

Answer 1

Correct option is (A) Twice the ratio of the energy stored in the magnetic field to the rate of dissipation of energy in the resistance.

For an L–R circuit,

T (time constant) = \(\left(\frac L R\right)\) 

Now energy stored in magnetic field is \(\frac12\)LI² and rate of dissipation of energy is I²R.