Generation of Electricity

Generation of Electricity

The National Grid

Definition: A network of high voltage power lines connecting all major power stations to homes and factories.

Power Stations in the UK

• The largest power stations use fossil fuels

• Coal

• Oil

• Gas

• Formed from the remains of organisms from millions of years ago.

• They are NON RENEWABLE

• Non- renewable: Can only be used once. Will not regenerate in your lifetime.

The National Grid

• Generators in a power stations produce electricity when a coil of wire is in a changing magnetic field.

• This changing magnetic field is caused by spinning a magnet inside the coil.

  
  

• Fossil fuel and nuclear power stations use the energy store to heat water and produce steam to turn a turbine which is connected to the magnet, causing it to spin.

Power Station

• Fossil fuels are used to heat water

• water turns to steam

• steam turns the turbine

• turbine turns the generator

• generator (large electromagnet) that induces a high potential difference (A.C)

• AC= Alternating Current

Leaving the power station

• 25KV leave the power station

• Step up transformer increases potential difference to 400KV (to minimise electrical energy loss as thermal energy due to the resistance of the electric cables)

• Travels along power lines until it reaches Step down transformer

• Step down transformer reduces p.d to safe 230/240 Volts for household use.

_{Safety features Live, neutral and earth mains wires}

• The UK mains supply is connected to appliances in the home by using a plug.

• The plug contains three wires ‐ the live, neutral and earth wires.

Plug safety

• In a plug, the live wire (brown) and the neutral wire (blue) are the two wires that form the complete circuit with a household appliance.

  
  

• The earth wire (green and yellow) does not normally form part of the circuit and is included as a safety wire. It is connected to 'earth', which is usually a large metal spike buried under a house.

The fuse

• A fuse is designed to melt if a current flows through it that is too large. For example, if a fuse has a rating of 3 A then it will melt if the current flowing through it exceeds 3 A. This is because if the current gets too high, too much heat could be produced which would cause the appliance to catch fire. Once the fuse melts, the circuit is broken and no current can flow.

Double insulation

• Devices which contain metal parts are surrounded with a casing that is made from a plastic insulation. This stops the user from coming into contact with any of the metal parts that conduct current. Coming into contact with these areas could cause electrocution.

The earth wire 

• This is designed so that a large current passes through the fuse in the event of the live wire loosening and touching a metal part of the appliance. If there were no earth wire, and a live wire were to loosen and touch a metal part of the appliance, someone touching the appliance would be electrocuted, as a high current would pass through the body to the ground (Earth).

Multiple Choice

A device has a rating of 6A. Which fuse would you use?

• 5A

• 13A

• 3A

Multiple Choice

A device has a rating of 4A. Which fuse would you use?

• 3A

• 5A

• 13A

Multiple Choice

A device has a rating of 0.5A. Which fuse would you use?

• 3A

• 5A

• 13A

Open Ended

What are the 3 fossil fuels?

Open Ended

Explain the term 'National Grid'

Open Ended

Why are step up transformers used to increase the voltage as the electricity leaves the power station?

Open Ended

In a plug, what is the function of an Earth wire?

Multiple Choice

What happens to a fuse if the current exceeds the rating of the device?

• it melts

• nothing

• it increases the current

• it decreases the current

Open Ended

Why are most devices insulation with plastic coating?