A hand-cranked generator transfers 42 J of energy to the chemical energy store of a rechargeable cell. It also transfers 7 J to its thermal energy store and 3 J by sound.
There are no other energy transfers.
How much energy is transferred mechanically to the generator?
32 J32\ \mathrm{J}32 J
49 J49\ \mathrm{J}49 J
52 J52\ \mathrm{J}52 J
45 J45\ \mathrm{J}45 J
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.