Past exam of the physics B course of the University of Cambridge 2011 Paper 2 Section A A1 Solution 2026-10-20
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.