The table shows the input energy and the wasted energy for four electric motors.
Table
| Motor | Input energy (J\text{J}J) | Wasted energy (J\text{J}J) |
|---|---|---|
| P | 800 | 200 |
| Q | 1200 | 360 |
| R | 500 | 100 |
| S | 2000 | 300 |
Which motor is the most efficient?
Motor P
Motor Q
Motor R
Motor S
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.