申論題

8. A student found a solenoid inductor made of thick resistive metal wire in the lab. This inductor is connected serially to a capacitor, initially charged with charge Q. When the switch is shorted, the decay of the charge on the capacitor is monitored and the time constant is determined to be τ. Next, the student unrolled the solenoid and stretched the metal wire homogeneously so that it became twice as long as it used to be. Then the student made a new solenoid with the 'stetched wire. The radius of the solenoid is the same as before, only the number of turns is changed.