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Paper 1
Energy Transfers & Efficiency
Both
Always show substitutions with units.
Key Facts
- Power in watts, energy in joules, time in seconds.
- Efficiency < 100% for real systems.
Key Equations
Power = energy / time
Work done = force × distance
Topics Covered
Power & Work
What you need to know
- •Power = energy transferred per second.
- •Work done = force × distance.
Exam Tips
- Convert time to seconds before calculating.
Efficiency
What you need to know
- •Efficiency is a decimal or percentage.
- •Useful output must be smaller than input.
Exam Tips
- Write efficiency as a percentage for the final answer.
Key Terms
Power
Rate of energy transfer or work done.
Efficiency
Useful output divided by total input.
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Common Exam Questions
Calculate power if 900 J is transferred in 30 s.
2 markseasyPaper 1
Model Answer
30 W
What examiners want to see
- ✓Use P = E / t and correct units.
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