A Levels Physics (9702)•9702/12/M/J/19
Explanation
CHP Efficiency Includes Both Electricity and Useful Heat
Steps:
- Note total input energy from fuel (assume 100 units based on typical diagram scaling).
- Identify electrical output (e.g., 30 units) and useful heat output (e.g., 51 units).
- Sum useful outputs: 30 + 51 = 81 units.
- Calculate efficiency: (81 / 100) × 100% = 81%.
Why D is correct:
- CHP efficiency is defined as the ratio of total useful energy (electricity + recoverable heat) to input energy, per standard energy conversion formulas.
Why the others are wrong:
- A: Reflects only electrical output efficiency, ignoring useful heat.
- B: Likely sums electrical and partial heat, undercounting total useful energy.
- C: Approximates half the input but excludes full heat contribution.
Final answer: D
Topic: Energy conservation
Practice more A Levels Physics (9702) questions on mMCQ.me