How is electricity generated, and how do energy resources compare?
Renewable and non-renewable energy resources, how power stations generate electricity, and the advantages and disadvantages of different resources.
A focused answer to WJEC GCSE Physics topic 1.2 on generating electricity, covering renewable and non-renewable energy resources, how power stations turn a turbine and generator, and the advantages and disadvantages of fossil fuels, nuclear and renewables.
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What this topic is asking
WJEC wants you to name renewable and non-renewable energy resources, describe how a power station generates electricity, and weigh up the advantages and disadvantages of the main resources. This is part of topic 1.2 Generating electricity in Unit 1 of WJEC GCSE Physics (3420).
Renewable and non-renewable resources
How a power station works
Wind, hydroelectric and tidal stations skip the heating stage: moving air or water turns the turbine directly.
Comparing the resources
When choosing a resource, engineers weigh up reliability, set-up and running cost, the carbon dioxide released, and the environmental impact such as habitat loss or visual intrusion.
Start-up time and meeting demand
Resources also differ in how quickly they can respond to a change in demand. Gas-fired stations can be started and stopped in minutes, so they are used to cover sudden peaks, for example when many people switch on kettles at the same time. Coal and nuclear stations take much longer to warm up and are run more steadily to provide a constant baseload. Among the renewables, hydroelectric stations are valuable because water held behind a dam can be released almost instantly to meet a surge in demand, while pumped storage schemes pump water uphill at off-peak times and release it when demand is high. Wind and solar cannot be controlled in this way, because their output depends on the weather and the time of day, which is why a real electricity supply uses a mix of resources rather than relying on any single one.
Try this
Q1. Name three renewable energy resources. [3 marks]
- Cue. Any three of wind, solar, hydroelectric, tidal, wave, geothermal, biomass.
Q2. State why nuclear power is described as low-carbon. [1 mark]
- Cue. It releases little or no carbon dioxide when generating electricity.
Exam-style practice questions
Practice questions written in the style of WJEC exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
WJEC 20193 marksDescribe the energy transfers in a coal-fired power station, from the fuel to the electricity output.Show worked answer →
A topic 1.2 Describe question. Burning coal releases chemical energy as thermal (heat) energy, which boils water to steam (1 mark). The steam turns a turbine, transferring energy to kinetic energy of the turbine and generator (1 mark). The spinning generator induces a voltage, transferring energy to electrical energy in the National Grid (1 mark). Markers reward the chemical to thermal to kinetic to electrical chain. A common error is to omit the turbine or to jump straight from heat to electricity.
WJEC 20224 marksCompare nuclear power and wind power as ways of generating electricity, giving one advantage and one disadvantage of each.Show worked answer →
A topic 1.2 Compare question. Nuclear: advantage, it produces a large, reliable output with no carbon dioxide from generation (1 mark); disadvantage, it produces radioactive waste that must be stored safely, and stations are expensive to build and decommission (1 mark). Wind: advantage, it is renewable and produces no carbon dioxide or fuel cost in use (1 mark); disadvantage, it is intermittent (only generates when the wind blows) and some find turbines visually intrusive (1 mark). Markers reward one valid advantage and one disadvantage for each, with a clear comparison.
Related dot points
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A focused answer to WJEC GCSE Physics topic 1.2 on the National Grid, covering how electricity is transmitted, the role of step-up and step-down transformers, and why a high transmission voltage and low current reduce the energy lost as heat in the cables.
- Energy stores and transfers, the conservation of energy, wasted energy, and the calculation of efficiency as the useful output over the total input.
A focused answer to WJEC GCSE Physics topic 1.3 on energy, covering energy stores and transfers, the conservation of energy, energy wasted as heat, and how to calculate efficiency as the useful energy or power output divided by the total input.
- Conduction, convection and radiation, the factors affecting heat loss, methods of insulating a house, and judging cost-effectiveness using payback time.
A focused answer to WJEC GCSE Physics topic 1.3 on making use of energy, covering conduction, convection and radiation, the factors affecting heat loss from a house, insulation methods, and how to compare them using cost-effectiveness and payback time.
- Electromagnetic induction, the a.c. generator, the transformer, the turns ratio and transformer equation, and why transformers are used in the National Grid.
A focused answer to WJEC GCSE Physics topic 1.9 on electromagnetic induction, covering how a generator induces an alternating voltage, how a transformer changes voltage using the turns ratio, the transformer equation, and why transformers matter for efficient transmission.
Sources & how we know this
- WJEC GCSE Physics specification (3420) from 2016 — WJEC (2016)