2. Produced by alternating voltages in which the positive and negative ends keep alternating
The UK mains supply is an ac supply at around 230 V
The frequency of the ac mains supply is 50 cycles per second or 50 Hz (hertz)
Direct current
Current that is always flowing in the same direction
Created by a direct voltage
Wires in most electrical appliances
Live wire
Neutral wire
Earth wire
Live wire
Provides the alternating potential difference (at about 230 V) from the mains supply
Neutral wire
Completes the circuit and carries away current electricity normally flows in through the live wire and out through the neutral wire (around 0 V)
Earth wire
For protecting the wiring and for safety - it stops the appliance casing from becoming live (0 V)
Your body is at 0 V
If you touch the live wire, a large potential difference is produced across your body and a current flows through you, causing an electric shock
Even if a plug socket or a light switch is turned off, there is still a danger of an electric shock as there is still a potential difference in the live wire
Any connection between live and earth can be dangerous as it can create a low resistance path to earth, resulting in a huge current flow which could cause a fire
Electricity is very useful, but it can also be very dangerous. Make sure you know the risks
