Conservation of energy and advantages and disadvantages of different producers of energy.

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Energy and electricity

Energy is measured in joules.

Conservation of energy means that the total amount of energy we put in equals the amount of energy we get out. E.G. 100j of energy is put into a light bulb. 10j light (useful) 90j heat (wasted).


The amount of useful energy stored at the end of the transfer compared to the the total amount of energy transferred is the efficiency. An efficient machine does not waste much energy. One way of showing this is via a sankey diagram.

The power of an appliance is the number of joules of energy transfers each second. The units for power are watts. 1 watt = 1 joule transfered every second. Joules are how much energy is produced. Joules = the measurement of energy.

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How is electricity generated?

Electricity is generated in power stations. Power stations need a resource, such as fossil fuels, nuclear fuels or a renewable source.

1. In many power stations fossil fuels are burnt. The energy is used to heat water and turn it into steam.

2. The steam is forced through large fans, called turbines, making them turn around.

3. The turbines turn generators. These are large magnets inside massive coils of wire. A moving magnet inside a coil of wire creates electricity (an electric current).

4. The electricity flows along cables called the national grid after going through the transformer.

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Volts and amps


The Voltage of a cell is a way of measuring how much energy the cell gives to the current. The voltage of a cell can measured using a voltmeter. The units for voltage are volts.


The size of an electric current is measured using an ammeter. The units are amps.

A good way to compare the two.

Here's a good analogy, say the wire is a road, the battery a bread factory and the light a super market, the current would therefore be the rate at which the vans leave the factory, and the voltage would be the amount of bread they're carrying (the energy). So amps are the rate at which energy is moved and volts are the actual level or intensity of that energy.

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