Two identical ceiling fans in a school hall are supplied with the same energy each second and run at the same setting. After an hour, the bearings of fan X are much hotter than the bearings of fan Y. Fan X also transfers less energy to the kinetic store of the air.
Which is the most likely explanation?
Fan X's bearings are poorly lubricated, so more work is done against friction.
Fan X's bearings have extra grease, so the grease transfers more energy by heating.
Friction in fan X's bearings creates extra energy, so the bearings warm up.
Fan X's wires have a higher resistance, so more energy is dissipated in its bearings.
100 exam-style questions on Edexcel GCSE Physics 3.2 Dissipation and efficiency, covering 3.2.1 Dissipation of energy, 3.2.2 Reducing unwanted energy transfers, 3.2.3 Efficiency, and 3.2.4 Increasing efficiency. Each one has a worked solution and a mark scheme showing where the marks go.