A device operates in two stages. The table shows the input energy and efficiency for each stage.
| Stage | Input energy in J\mathrm{J}J | Efficiency |
|---|---|---|
| P | 200 | 80% |
| Q | 800 | 50% |
The stages receive energy separately from the supply.
What is the efficiency for the complete operation?
40%40\%40%
65%65\%65%
56%56\%56%
74%74\%74%
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.