Question

A resistor held in running water carries electric current. Treat the resistor as the system (a) Does heat flow into the resistor? (b) Is there a flow of heat into the water?  (c) Is any work done? (d) Assuming the state of resistance to remain unchanged,  apply the first law of thermodynamics to this process.

Answer 1

(a) As electric current is passing through the resistor which heats up the resistor, we can say that heat is being supplied to the resistor.

(b) Since water is flowing over the resistor, some heat will be transferred to the water. Hence there is a flow of heat into the water.

(c) Since there is no change in volume, no work is done. Work done is given by W = p dV. Here \(\triangle V\) = 0.