Solution

ID: past-exam-of-the-physics-b-course-of-the-university-of-cambridge/2011/paper-2/section-a/a1/solution

For the entropy balance of a thermostatted resistor, electrical work becomes heat . At fixed temperature the resistor has no net change of thermodynamic state; it exports this heat to its thermostat. Treating the electrical supply as a source of work,
Entropy is produced by Joule heating even though it does not accumulate in the resistor. Additional entropy production inside a nonideal power supply is outside the specified model.

New to topics? Read the docs here!