A wind turbine converts kinetic energy from moving air into electrical energy. Some energy is dissipated as heat due to friction in the turbine's moving parts and resistance in its electrical components. Explain how the efficiency of the wind turbine could be improved, and explain what is meant by efficiency in this context.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A wind turbine is used to generate electricity for a remote farmhouse. Engineers are looking for ways to make the turbine operate more efficiently.
Model answer (4 marks)
Efficiency is the ratio of useful output energy transfer to total energy input. It can never exceed 1 (or 100 %) because energy cannot be created or destroyed (conservation of energy). The efficiency of the wind turbine could be improved by lubricating the moving parts to reduce friction, which lowers the heat energy dissipated as waste. It could also be improved by reducing the current in the electrical components, which decreases power lost as heat in the wires (power loss = I²R).
Examiner tips
- Define efficiency as a ratio of useful output to input energy
- Explain the 100 % limit using conservation of energy
- Mention lubrication to reduce friction and heat
- Show the I²R loss formula for electrical resistance
Common mistakes
- Using the wrong definition of efficiency (e.g. energy in vs. energy out only)
- Forgetting that efficiency cannot exceed 100 %
- Failing to mention the I²R loss or lubrication as specific improvement methods
Mark scheme (4 marks)
- Efficiency is the ratio of useful output energy transfer to total energy input
- Efficiency can never exceed 1 (or 100%) because energy cannot be created or destroyed (conservation of energy)
- Lubrication of the moving parts reduces friction, which reduces heat energy dissipated as waste
- Reducing current in the electrical components decreases power lost as heat in the wires (power loss = I²R), improving efficiency
Key terms in this question
Related
- All OCR GCSE Physics A: Gateway Science (J249) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
More Power and efficiency questions
- A food blender is used in a kitchen to blend ingredients. The blender transfers …
- A cyclist rides along a flat road. The cyclist's legs exert a force to turn the …
- A swimming pool uses an electric pump to circulate water through a heating syste…
- A factory uses an electric motor to lift heavy crates. The motor has a power rat…