IGCSE Physics / Energy resources and electricity generation
Generating electricity: fossil fuels and nuclear power revision notes
Edexcel International GCSE Physics (4PH1), chapter 17: Energy resources and electricity generation, specification point 4.18P. Free lesson.
Watch the video lesson · IGCSE Physics past papers
Fossil-fuel and nuclear power stations heat water to make steam, which turns a turbine and generator. Their main difference is how they release energy to heat the water.
How a fossil-fuel power station works
Coal, oil and gas stations use the same main parts in the same order. Fuel burns in the furnace, and the energy heats water in the boiler until it becomes high-pressure steam. The steam spins the turbine, which turns the generator and produces a current. Cables carry electricity to homes and industry. In the condenser, steam leaving the turbine is cooled back into water. Cooling water carries waste energy away. A turbine is a shaft covered in blades. Steam rushing through it makes it spin.
How energy is transferred through the station
To describe the energy transfers, follow the energy stores in order. The fuel starts with energy in its chemical store. Burning transfers energy by heating to the thermal store of the water, which becomes steam. Moving steam transfers energy mechanically to the kinetic store of the turbine. The turbine turns the generator, which transfers energy electrically. Some energy is wasted by heating the thermal store of the surroundings, so the station is not one hundred per cent efficient. Chemical store of the fuel → thermal store of the water and steam → kinetic store of the turbine →…
How nuclear power stations are different
A nuclear station uses the same stages after the water is heated. The difference is the fuel and how its energy is released. Fossil fuels have energy in a chemical store and release it by burning. Uranium or plutonium has energy in a nuclear store, released by fission: a large nucleus splits into two smaller nuclei. The reactor takes the place of the furnace and heats the water. Steam then drives a turbine, which turns a generator.
Use the right word for fission
Fission happens in the nucleus, the tiny centre of an atom. In an answer, say that a uranium nucleus splits into two smaller nuclei, releasing energy. Saying that uranium atoms split is inaccurate and can lose you a mark.
Describe energy transfers for four marks
Name each store with the object it belongs to, keep the transfers in the right order, and include wasted energy. For a gas-fired station, the sequence is:
Compare nuclear and coal-fired stations
Both types heat water to make steam. In each station, steam drives a turbine and the turbine turns a generator. Their difference is before the steam is made: coal burns, while nuclear fuel releases energy from its nuclear store by fission.