The chain on a cyclist's bicycle is rusty. The chain squeaks when the bicycle is ridden.
Explain why a rusty chain wastes energy.
The cyclist puts oil on the chain.
Explain how this reduces the unwanted energy transfer.
The Table shows the energy transferred when the cyclist rides the same distance before and after oiling the chain.
Table
| Quantity | Before oiling | After oiling |
|---|---|---|
| Energy transferred by the cyclist in J\text{J}J | 3200 | 3200 |
| Energy transferred to the kinetic store of the bicycle in J\text{J}J | 2400 | 2880 |
Calculate the increase in the efficiency of the bicycle after the chain is oiled.
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.