Problem 3.318

Calculate the time constant $\tau$ of a straight solenoid of length $l=1.0 \mathrm{~m}$ having a single-layer winding of copper wire whose total mass is equal to $m=1.0$ kg. The cross-sectional diameter of the solenoid is assumed to be considerably less than its length.

Note. The time constant $\tau$ is the ratio $L / R,$ where $L$ is inductance and $R$ is active resistance.