GCSE Physics Energy resources revision

Almost every electricity resource ends the same way: the energy turns a turbine, which spins a generator. Fossil and nuclear stations boil water into high-pressure steam; hydro drops water through turbines; wind uses the air itself. Solar panels are the exception — photovoltaic cells convert light directly into electricity with no moving parts. Geothermal uses hot rock to make steam where the geology allows it.

Electricity is used the instant it is generated, so the National Grid must match supply to demand second by second. Reliable resources (fossil, nuclear, hydro with a reservoir, geothermal) can be turned up when demand peaks — a famous moment is the surge when millions put kettles on at half-time in a big match. Unreliable resources depend on nature: wind needs wind, solar needs daylight (and more of it in summer), waves need storms offshore. Tides are the special case: completely predictable but intermittent — the tide comes when the Moon says, not when demand says.

• Reservoirs store energy: pumped-storage stations use spare night-time electricity to pump water uphill, releasing it through turbines when demand spikes.
• Biomass is dispatchable: biofuel can be burned exactly when needed, like coal.
• Back-up is still needed: because wind and solar fluctuate, gas stations or storage must fill the gaps on calm, dull days.
• Forecasting helps: the grid predicts wind and sunshine hours ahead and plans around them.

Burning fossil fuels releases carbon dioxide, the main greenhouse gas behind global warming and climate change, and sulfur dioxide, which causes acid rain. Coal mining scarred landscapes and communities; oil drilling and transport risk spills; gas extraction raises questions about ground water where fracking is used. Nuclear stations emit no carbon dioxide while running, but their spent fuel stays radioactive for thousands of years and the stations themselves must be decommissioned — dismantled and cleaned up — at great cost. Renewables have their own bills: wind turbines change skylines and can be noisy up close; hydroelectric dams flood valleys and destroy habitats; solar farms cover land; tidal barrages alter whole estuaries. A good evaluation quotes an advantage and a disadvantage as a pair, then reaches a judgement for the stated use.

Examiners love asking you to describe the trend and suggest why: renewables grew because their costs fell, because of government targets on carbon emissions, and because ageing fossil and nuclear stations closed. Note that the transport sector changed much more slowly — petrol and diesel still dominate vehicles, though electric cars charged from a greener grid are rising fast.

A kilowatt-hour is the energy transferred by a 1 kW appliance running for 1 hour: 1 kWh = 1 000 W × 3 600 s = 3 600 000 J (3.6 MJ). Electricity meters count kWh; suppliers charge pence per kWh. The same reasoning audits gas bills (measured in kWh of heat) and the running costs of every appliance you own. Typical UK homes use roughly 8–10 kWh of electricity a day, more in winter with heating and lighting.