P5

• what is A.C.?

  Alternating current which means the direction of the current is constantly changing
• The UK mains supply is A.C. It has a PD of 230V and a frequency of 50 Hz
• What is D.C. ?

  Direct current - batteries supply direct current and the direction of flow never changes
• What is a fuse?

  A very thin piece of wire that melts when too much current flows through it meaning that all current will stop and the appliance will turn off. It protects from electrical fires
• Fuse's should have a fuse rating slightly higher than the operational current of the appliance. To determine the operational current and correct fuse you can use the V=IxR equation
• What are the 3 wires that enter a plug?

  Live, Neutral and Earth
• What does the live wire do?

  Provides the potential difference from the mains
• What does the neutral wire do?

  Completes the circuit
• What does the Earth wire do?

  Stops the appliance from becoming live therefore protects against electric shocks
• What colour are each of the wires in a plug?

  Neutral = blue

  Live = brown

  Earth = yellow and green stripes
• Where is each wire positioned in a plug?

  Neutral = bottom left

  Live = bottom right

  Earth = top middle

  
• Electrical wires are made from copper as this is the most effective electrical conductor
• The pins in a plug are made from brass as it is not a flexible material but is still a good conductor
• The casing of the plug is made of plastic as it's rigid and does not conduct electricity
• Define power

  The rate of transfer of energy and is measure in Watts
• What is the national grid?

  A system of overhead cables and transformers that deliver electrical power from stations to where it is needed.
• Electricity is transferred at a low current but a high PD as this lowers resistance in the long wires. This means that less energy is dissipated to the surroundings
• What do step up transformers do?

  Increase the PD and decrease the current. They are normally found by power stations
• What do step down transformers do?

  Decrease the PD and increase the current to make it safe for consumer use