OCR GCSE Physics A (Gateway)
OCR GCSE Physics A P8.2 Powering Earth Exam Questions
Free OCR GCSE Physics A exam questions for P8.2 Powering Earth, with a mark scheme for every pack. Covers energy resources, renewable and non-renewable sources, the National Grid, transformers, mains electricity, live, neutral and earth wires and energy use.
P8.2 Powering Earth exam questions
1 question pack 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 OCR GCSE Physics A P8.2 Powering Earth
P8.2 is part of the P8 Global challenges chapter of OCR Gateway Physics A. It looks at how society meets its energy needs. You compare renewable and non-renewable energy resources for transport, electricity generation and heating, and evaluate their reliability and environmental impact. You explain how the National Grid uses step-up and step-down transformers to transmit electricity efficiently, and describe domestic mains electricity, including the live, neutral and earth wires and why the live wire can be dangerous. It draws on P3 Electricity, P4 Magnetism and P7 Energy, so questions are often synoptic. Examiners like six-mark evaluations of energy resources and National Grid explanations.
What you need to know
- Energy resources Non-renewable: fossil fuels (coal, oil, gas) and nuclear fuel. Renewable: wind, solar, hydroelectric, tidal, waves, geothermal, bio-fuel. Compare them by reliability, cost, carbon dioxide emissions and environmental impact.
- Patterns of use Use of fossil fuels for electricity is falling as more renewables are used, but changes are affected by cost, politics and reliability.
- National Grid A network of cables and transformers linking power stations to consumers. Step-up transformers raise the p.d. to reduce the current and so reduce heating losses in cables; step-down transformers lower the p.d. for homes.
- Transformer power For a 100% efficient transformer, potential difference across primary x current in primary = potential difference across secondary x current in secondary.
- Mains electricity UK mains supply is a.c. at about 230 V and 50 Hz. Live wire (brown) is at a high p.d.; neutral (blue) is near 0 V; earth (green and yellow) is a safety wire.
- Dangers of the live wire Touching the live wire can give a fatal shock because your body is at 0 V, so a current flows through you to earth, even if the switch is off and the circuit is not complete.
Common mistakes in P8.2 Powering Earth
- Saying high voltage reduces energy loss directly. It is the lower current that reduces heating of the cables.
- Saying renewable resources are always reliable. Wind and solar depend on weather and time of day.
- Confusing the colours of the wires. Live is brown, neutral blue, earth green and yellow.
- Saying the neutral wire is dangerous. The live wire is at a high p.d. and is the dangerous one.
- Saying nuclear power is renewable.
Try three P8.2 Powering Earth exam-style questions
1. A transformer is 100% efficient. The primary p.d. is 11 500 V and the primary current is 4.0 A. The secondary p.d. is 230 V. Calculate the secondary current. (3 marks)
Show the mark scheme answer
Vp x Ip = Vs x Is; 11 500 x 4.0 = 230 x Is; Is = 46 000 / 230 = 200 A.
2. Explain why electricity is transmitted in the National Grid at a very high p.d. (3 marks)
Show the mark scheme answer
For a given power, higher p.d. means lower current; lower current causes less heating in the cables; so less energy is wasted and transmission is more efficient.
3. Explain why touching a live wire is dangerous even when an appliance is switched off. (2 marks)
Show the mark scheme answer
The live wire is still at a high p.d. (about 230 V) while the person is at 0 V (earth potential); so a large current can flow through the person to earth, causing a shock.
P8.2 Powering Earth FAQs
What does OCR GCSE Physics A (Gateway Science) P8.2 Powering Earth cover?
It covers energy resources, trends in energy use, the National Grid, transformers and mains electricity including the live, neutral and earth wires.
Which paper is P8.2 examined on?
Topics P5 to P8 are assessed on Paper 2 (Foundation) or Paper 4 (Higher), which can also draw on knowledge from P1 to P4 and practical skills.
How do I write a good energy resources evaluation?
Compare at least two resources using reliability, cost, renewability and environmental impact, give an advantage and a disadvantage for each, and finish with a justified conclusion.
