Edexcel GCSE Physics
Edexcel GCSE Physics Topic 3: Conservation of Energy Exam Questions
Free Edexcel GCSE Physics exam questions for Topic 3: Conservation of Energy, with a mark scheme for every pack. Covers energy stores and transfers, conservation of energy, kinetic and gravitational potential energy, efficiency, insulation and energy resources.
Topic 3: Conservation of Energy exam questions
2 question packs of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About Edexcel GCSE Physics Topic 3: Conservation of Energy
Topic 3 on Paper 1 introduces the idea that energy is never created or destroyed, only transferred between stores. You learn the main energy stores, how to calculate changes in gravitational potential energy and kinetic energy, how energy is dissipated, and how to calculate efficiency. The separate physics course adds a core practical on thermal insulation. The topic ends with renewable and non-renewable energy resources and how their use is changing. It links to Topic 8, where energy is transferred by forces doing work, and Topic 14 on thermal energy. Examiners commonly set GPE to KE calculations, efficiency questions and six-mark comparisons of energy resources.
What you need to know
- Energy stores Energy can be stored as kinetic, gravitational potential, elastic, thermal, chemical, magnetic, electrostatic and nuclear energy. It is transferred mechanically, electrically, by heating or by radiation.
- Conservation of energy Energy cannot be created or destroyed. In a closed system the total energy stays the same, although some is usually dissipated to the surroundings as thermal energy.
- GPE and KE Change in GPE = m x g x change in h. KE = 1/2 x m x v^2. For a falling object with no air resistance, the loss in GPE equals the gain in KE.
- Efficiency Efficiency = useful energy transferred / total energy supplied, as a decimal or percentage. Lubrication reduces friction and insulation reduces unwanted heat transfer, increasing efficiency.
- Thermal insulation The rate of energy transfer through a wall depends on its thickness and thermal conductivity. Thicker walls and materials with low thermal conductivity reduce heat loss from buildings.
- Energy resources Non-renewable: coal, oil, gas, nuclear. Renewable: wind, solar, hydroelectric, tidal, waves, biofuels, geothermal. Compare reliability, cost, environmental impact and carbon dioxide emissions.
Common mistakes in Topic 3: Conservation of Energy
- Saying energy is lost or used up. Say it is transferred or dissipated to the surroundings, usually as thermal energy.
- Forgetting to square the velocity in KE = 1/2 x m x v^2, or squaring the whole of 1/2 x m x v.
- Giving an efficiency greater than 1 or 100%. If you get this, you have divided the wrong way round.
- Calling nuclear fuel renewable because it produces no carbon dioxide while generating. Uranium is non-renewable because it will run out.
- Saying a material with high thermal conductivity is a good insulator. Good insulators have low thermal conductivity.
Try three Topic 3: Conservation of Energy exam-style questions
1. A ball of mass 0.20 kg is dropped from a height of 5.0 m. Ignoring air resistance, calculate its speed just before it hits the ground. Use g = 10 N/kg. (4 marks)
Show the mark scheme answer
GPE lost = m x g x h = 0.20 x 10 x 5.0 = 10 J; KE gained = 10 J; 10 = 1/2 x 0.20 x v^2 so v^2 = 100; v = 10 m/s.
2. A motor is supplied with 400 J and transfers 120 J usefully. Calculate its efficiency. (2 marks)
Show the mark scheme answer
Efficiency = useful energy / total energy = 120 / 400; = 0.30 or 30%.
3. Explain one advantage and one disadvantage of using wind turbines to generate electricity. (4 marks)
Show the mark scheme answer
Advantage: renewable, will not run out; produces no carbon dioxide while generating. Disadvantage: unreliable because output depends on wind speed; so backup supplies are needed (or visual and noise impact).
Topic 3: Conservation of Energy FAQs
What does Edexcel GCSE Physics Topic 3 Conservation of Energy cover?
It covers energy stores and transfers, the conservation of energy, GPE and KE calculations, efficiency, thermal insulation and energy resources.
Which paper is Topic 3 examined on?
Topic 3 is assessed on Paper 1.
What equations do I need for Conservation of Energy?
You need change in GPE = m x g x change in h, KE = 1/2 x m x v^2 and efficiency = useful energy transferred / total energy supplied.
