OCR - P2: Sustainable energy

P2.2 How can electricity be generated?
Background to the topic What you should be able to do:

The main energy resources that are available to humans are fossil fuels (oil, gas, coal), nuclear fuels, biofuels, wind, hydroelectric, tides and from the Sun.

In most power stations generators produce a voltage across a wire by spinning a magnet near the wire.

Often an energy source is used to heat water; the steam produced drives a turbine which is coupled to an electrical generator.

Other energy sources drive the generator directly.

The mains supply to our homes is an alternating voltage, at 50 Hz, 230 volts, but electricity is distributed through the National Grid at much higher voltages to reduce energy losses.

Transformers are used to increase the voltage for transmission and then decrease the voltage for domestic use.

Most mains appliances are connected by a 3 core cable, containing live, neutral and earth wires.

The demand for energy is continually increasing and this raises issues about the availability and sustainability of energy sources and the environmental effects of using these sources.

The introduction and development of new energy sources may provide new opportunities but also introduce technological and environmental challenges. The decisions about the energy sources that are used may be different for different people in different contexts

1. Describe the main energy resources available for use on Earth (including fossil fuels (oil, gas, coal), nuclear fuels, biofuels, wind, hydroelectric, tides and also from the Sun).

2. Explain the differences between renewable and nonrenewable energy resources

3. Compare the ways in which the main energy resources are used to generate electricity

4. Recall that the domestic supply in the UK is a.c., at 50 Hz and about 230 volts and explain the difference between direct and alternating voltage

5.Recall that, in the National Grid, transformers are used to transfer electrical power at high voltages from power stations, to the network and then used again to transfer power at lower voltages in each locality for domestic use

6. Recall the differences in function between the live, neutral and earth mains wires, and the potential differences between these wires; hence explain that a live wire may be dangerous even when a switch in a mains circuit is open, and explain the dangers of providing any connection between the live wire and any earthed object

7. Explain patterns and trends in the use of energy resources in domestic contexts, workplace contexts, and national contexts