A leisure centre uses an electric heater to warm the water in an outdoor swimming pool. Energy transferred to the thermal energy store of the pool water is the intended useful output. A floating cover is placed over the pool while the heater operates. The heater is supplied with the same amount of electrical energy in each heating period, whether or not the cover is used.
Explain why the ratio of useful energy transferred to total energy supplied is greater when the floating cover is used.
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.