A useful starter to the study of electricity is to look at how we use electricity in the home. We use it all the time and when we plug an appliance in, we just take it for granted that the appliance is going to work. However, we should remember to treat electricity with respect as it has the (if you'll pardon the pun) potential to be very dangerous indeed.


There are two types of electricity, alternating current (AC) and direct current (DC). The type that we use in the home is alternating current and in the UK this operates at around 230 to 240 V.



  • The brown wire is the wire which provides the alternating potential difference at approximately 230 V from the mains supply.
  • The blue wire is the neutral wire, this completes the circuit at approximately 0 V.
  • The yellow/green two coloured wire is the earth wire, also at 0 V and is therefore safety reasons. Should the be an electrical malfunction the purpose of this wire is to carry the current safely away, preventing the appliance itself from becoming live.


In an alternating current supply, the current is constantly changing direction as a result of alternating voltages, and this happens at approximately 50 times a second which is why you're sometimes hear domestic electricity suppliers in the UK being described as 50 Hz or 50 cycles per second.


Not on syllabus:


The fuse is selected according to the requirements of the appliance. An appliance which draws a heavy load, for example an electric kettle or washing machine will require a fuse with a higher current rating (usually thirteen amp). Devices taking a medium load will take a lower rated fuse, perhaps a five amp or a three amp.




At the present time, fuses are also colour-coded to add recognition. Three amp fuses are red, five amp fuses are black and thirteen amp fuses are brown.