In the UK, electrical appliances connect to the mains using a three-pin plug. Each pin is connected to a wire with a unique colour, making it easy to identify.
The features of a plug are shown below.
Each wire, made of copper, is designed to conduct electricity. For safety, they are coated in a layer of insulating plastic. Let’s look at an actual plug:
The table below highlights the properties of each of the 3 wires.
|Live||Carries the alternating potential difference from the power supply.||Brown|
|Neutral||Takes the electric current back to the source to complete the circuit.||Blue|
|Earth||Acts as the safety wire.|
An electrical fault in the circuit can occur if the live wire becomes loose and touches the casing.
To prevent this, the Earth wire provides an alternative path for the current to flow. However, this action also prevents the appliance from operating.
|Green and yellow|
As you can see in the table below, the potential difference between the live wire and both the neutral wire and the earth wires is 230 V.
|Wires||Potential difference between them (V)|
|Live and neutral||230|
|Live and earth||230|
|Neutral and earth||0|
The current can flow between the live and the neutral or earth wire because the potential difference between them is 230 volts
The human body is typically at 0 V, which makes the live wire very dangerous, as there is a large potential difference between the live wire and the human body. Therefore, a large current can pass through the human body to the earth, causing a significant electric shock.