WJEC GCSE Physics
WJEC GCSE Physics 1.2 Generating Electricity Exam Questions
Free WJEC GCSE Physics revision for 1.2 Generating Electricity: what you need to know, common mistakes and exam-style questions with answers. Covers renewable and non-renewable energy sources, power stations, Sankey diagrams, efficiency, the National Grid and transformers.
Practise 1.2 Generating Electricity with past papers
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About WJEC GCSE Physics 1.2 Generating Electricity
Generating electricity in Unit 1 compares the ways electricity is produced and delivered. You need the advantages and disadvantages of renewable sources such as wind, wave, tidal, hydroelectric, solar and biomass, and of fossil fuels and nuclear power. You must describe the energy changes in a fuel-based power station, draw and interpret Sankey diagrams, and calculate efficiency. The topic explains why the National Grid transmits at very high voltages using step-up and step-down transformers, and how supply is matched to demand. Examiners often ask you to evaluate different power stations using data on efficiency, reliability, carbon footprint and output.
What you need to know
- Energy sources Renewables (wind, wave, tidal, hydroelectric, solar, biomass, waste) will not run out and produce little carbon dioxide in use, but some are unreliable or have low output. Fossil fuels are reliable but produce carbon dioxide; nuclear produces no carbon dioxide in use but creates long-lived radioactive waste.
- Power stations In a fuel-based power station, burning fuel heats water to make steam, which turns a turbine connected to a generator. Energy is wasted as heat at each stage, particularly in cooling.
- Sankey diagrams and efficiency Arrow widths represent energy. Efficiency = useful energy (or power) output / total energy (or power) input x 100%.
- National Grid The Grid connects power stations to consumers and allows supply to be switched to meet changing demand. Output must be monitored and increased quickly at peak times.
- High voltage transmission For a given power, P = VI, so a higher voltage means a lower current. Lower current means less heating of the cables and less energy wasted. Step-up transformers increase voltage at power stations; step-down transformers reduce it for homes.
- Comparing stations Use data on efficiency, reliability, carbon footprint, cost and output to judge which type of power station suits a situation.
Common mistakes in 1.2 Generating Electricity
- Saying high voltage transmission is safer. High voltage is dangerous; it is used because the lower current reduces heating losses in the cables.
- Giving efficiency as a number greater than 100% or forgetting it cannot be. Check you have divided useful output by total input.
- Calling nuclear power renewable. Uranium is a finite fuel, so nuclear power is non-renewable, even though it releases little carbon dioxide.
- Writing that renewables are always unreliable. Hydroelectric and tidal output can be predicted or controlled; wind and solar depend on the weather.
Try three 1.2 Generating Electricity exam-style questions
1. A power station receives 2000 MJ of energy from fuel and supplies 700 MJ of electrical energy. Calculate its efficiency. (2 marks)
Show the mark scheme answer
700 / 2000 x 100; = 35%.
2. Explain why electricity is transmitted across the National Grid at high voltage. (3 marks)
Show the mark scheme answer
For the same power, P = VI so higher voltage means lower current; lower current means less heating in cables; less energy wasted / greater efficiency.
3. Give one advantage and one disadvantage of tidal power. (2 marks)
Show the mark scheme answer
Advantage: renewable / no carbon dioxide in use / predictable; disadvantage: high building cost / damages estuary habitats / output varies with tides.
1.2 Generating Electricity FAQs
What does WJEC GCSE Physics 1.2 Generating Electricity cover?
It covers renewable and non-renewable energy sources, how power stations work, Sankey diagrams, efficiency, the National Grid, high voltage transmission and the role of transformers.
Which unit is Generating Electricity examined in?
It is examined in Unit 1: Electricity, Energy and Waves, a 1 hour 45 minute written paper worth 45% of the GCSE, sat at foundation or higher tier. The Unit 3 practical assessment draws on the same practical skills.
How do I answer evaluation questions on power stations?
Use the data given, compare at least two factors such as reliability and carbon dioxide emissions, and finish with a clear judgement. Generic statements without data rarely gain full marks.
