Two resistive solenoids are made of same geometry and same number of turns per unit length. Copper wire used to make the solenoids are having different radius of cross section. Which of the following quantities are different for solenoids?

Options

A. Time constant if both the solenoids are connected to identical batteries
B. Rate of joules heating when same current is passed through the solenoids
C. Magnetic field energy stored in solenoids when same current is passed through the solenoids
D. Self-inductance

Answer

A, B

Explanation

Self-inductance is independent of radius of wire used to make it. Hence self-inductance for both is the same, hence option (d) is wrong. Energy stored in the 1 solenoid is given by `U = (1)/(2)Li^(2)` hence energy stored in 2 both the solenoids is going to be same when same current is passed through both the solenoids. Hence, option (c) is wrong. Radius of cross section of wire affects the resistance of coil and hence it affects time constant of the circuit and rate of heat dissipation when same current is passed through them. Hence, options (a) and (b) are correct.