A wire in the form of a tightly wound solenoid is connected to a DC source, and carries a current. If the coil is stretched so that there are gaps between successive elements of the spiral coil, will the current increase or decrease? Explain.

If the solenoid is stretched, then the current drawn from the DC source will be more compared to the current drawn from the DC source when the wire is twisted like a solenoid. If the wire is stretched, then the air gaps will be reduced. So no wastage of flux. In case of stretched wire, the air gaps in the successive elements will be more. So there is a lot of wastage for stretched wire.