Look at the information in the table about different electric winches used in a warehouse:
| Electric winch | Energy input per minute (kJ) | Useful energy output per minute (kJ) | Energy 'wasted' per minute (kJ) |
|---|---|---|---|
| P | 120 | 96 | |
| Q | 90 | 63 | |
| R | 45 | 6 | |
| S | 84 | 28 | |
| T | 75 | 62 |
Calculate the energy input per minute in kJ\text{kJ}kJ for electric winch S.
Which electric winch has the lowest 'wasted' energy in one minute?
Which electric winch has the highest 'wasted' energy in one minute?
Describe how energy is 'wasted' in an electric winch.
Suggest how this 'wasted' energy can be reduced in an electric winch.
Calculate the % efficiency of electric winch T. Use the equation:
Efficiency=Useful output energy transferInput energy transfer×100% \text{Efficiency} = \frac{\text{Useful output energy transfer}}{\text{Input energy transfer}} \times 100\% Efficiency=Input energy transferUseful output energy transfer×100%Give your answer to 2 significant figures.
37 exam-style questions on OCR GCSE Physics Power and efficiency. Each one has a worked solution and a mark scheme showing where the marks go.