ENERGY AND ELECTRICITY

Energy can be stored or transferred from place to place in different ways. Let's look at some examples.

eg: 

Kinetic - movement, Sound - vibrating drum, Thermal - heat, Chemical - stored, Electrical - stored, Gravitataional - stored, Elastic - rubber band

Energy transfer diagrams show the locations of energy stores and energy transfers. For example, consider the energy transfers in the simple electrical circuit below.

We can show the transfers like this:

The battery is a store of chemical energy. The energy is transferred by electricity to the lamp, which transfers the energy to the surroundings by light. These are the useful energy transfers - we use electric lamps to light up our rooms.

But there are also energy transfers that are not useful to us. In the example above, the lamp also transfers energy to the surroundings byheating. If we include this energy transfer, the diagram looks like this:

Sankey diagrams

Sankey diagrams summarise all the energy transfers taking place in a process. The thicker the line or arrow, the greater the amount of energy involved. This Sankey diagram for the lamp shows that it transfers most of the energy by heating, rather than by light:

Notice that the total amount of energy transferred to the surroundings is the same as the amount of electrical energy. We say that the energy has been conserved. Energy is always conserved, it is never "lost" or "wasted", although some energy transfers are useful and some are not.

Generating electricity

Electricity can be generated in many ways, including:

• in power stations using fossil fuels or biomass fuel

• using wind turbines

• using hydroelectric power schemes

• using wave power or tidal power.

• using solar cells.

Most of the UK's electricity is generated in power stations using fossil fuels. Thermal energy released from the burning fuel is used to boil water to make steam, which expands and turns turbines. These drive the generators to produce electricity.

1. the fuel is burned to boil water to make steam

2. the steam makes a turbine spin

3. the spinning turbine turns a generator which produces electricity

4. the electricity goes to the transformers to produce the correct voltage

As the fossil fuels are non-renewable energy resources, and they also produce pollution when they burn, we are aiming to produce more of our electricity using other, renewable energy resources. This will reduce the rate at which the fossil fuels are used up.

Electric circuits can be series or parallel. You need to know the symbols we use to draw circuit diagrams.

An ammeter measures electric current, in amps, by measuring how much charge is flowing in the circuit. A voltmeter measures, in volts, the difference in electrical energy between two points of a circuit.

Electric current

When electric charges move in a wire, we say that an electric currentflows in the wire. It's like the way a current of water flows in a river.

For an electric current to flow, we need two things:

• something to make…