Quick answer: Efficiency is the fraction of the total input energy that becomes useful output: efficiency = useful output ÷ total input, often shown as a percentage. This Physics 9-10 test on energy efficiency has 8 questions worth 20 marks, to do in 40 minutes: energy stores, conservation and water pump. The mark scheme is on a separate page; free printable PDF.
This test checks your knowledge of energy stores, conservation, Sankey diagrams and efficiency. Show your working for every calculation and include units. Use g = 9.8 N/kg. The total is 20 marks.
Level: Physics grades 9-10 (GCSE · IGCSE · O Level · Class 9-10) · Curriculum: GCSE P1, HS-PS3-4
Question 1 Energy stores (2 marks)
Name the main energy store in each case.- A stretched spring. (1 mark)
- Petrol in a tank. (1 mark)
Question 2 Conservation (1 mark)
State the principle of conservation of energy. (1 mark)Question 3 Water pump (3 marks)
A pump motor takes in 2500 J of electrical energy and gives out 1750 J of useful energy.- Calculate the wasted energy. (1 mark)
- Calculate the efficiency as a percentage. (2 marks)
Question 4 Electric drill (4 marks)
The Sankey diagram shows the energy flow for an electric drill.- Calculate the energy wasted as sound. (1 mark)
- Calculate the efficiency of the drill. (2 marks)
- State what happens to the wasted energy. (1 mark)
Question 5 Boiler (3 marks)
A boiler is 80 % efficient and delivers 24 MJ of useful thermal energy.- Calculate the energy input from the fuel. (2 marks)
- Calculate the energy wasted. (1 mark)
Question 6 Reducing waste at home (3 marks)
A family wants to reduce wasted thermal energy in their house.- Name two measures they could take. (2 marks)
- Explain how one of your measures reduces the energy wasted. (1 mark)
Question 7 Two machines (3 marks)
Machine A takes in 500 J and gives out 400 J of useful energy. Machine B takes in 800 J and gives out 600 J of useful energy.- Calculate the efficiency of each machine. (2 marks)
- State which machine is more efficient. (1 mark)
Question 8 Impossible claim (1 mark)
An inventor says a machine is 105 % efficient. Explain why this is impossible. (1 mark)
