An electric kettle is used to boil some water.
Which energy transfer is wasted?
Energy transferred electrically from the mains to the heating element
Energy transferred by heating from the heating element to the water
Energy transferred by heating from the kettle to the air around it
Energy transferred to the thermal store of the water as it heats up
50 exam-style questions on OCR GCSE Physics 7.2 Power and efficiency, covering 7.2.1 Dissipation of energy, 7.2.2 Energy transfers in domestic devices, 7.2.3 Power ratings of domestic appliances, 7.2.4 Efficiency of energy transfers, 7.2.5 Ways to increase efficiency, 7.2.6 Reducing unwanted energy transfers, and 7.2.7 Thermal conductivity and the cooling of buildings. Each one has a worked solution and a mark scheme showing where the marks go.