2.3 Understand the uses of insulation, double insulation, earthing, fuses and circuit breakers in a range of domestic appliances

• Insulation prevents the current from flowing anywhere but the metal wires where it is supposed to flow. An insulator is something that does not conduct electricity and is therefore a non metal. These protective 'tubes' cover the live wires. (if you have no idea what I'm talking about, see figure 2. The primary insulation is the insulation I'm talking about. In this case specifically, there would be no secondary insulation.)

Figure 1

Figure 2

• Double insulation makes sure that live wires do not conduct through the casing of a component. This is usually when it has a metal casing. Normally, it means putting extra insulation around that wire (see the white in figure 1) (see secondary insulation in figure 2). It can also mean that the casing of an object is plastic or another non-conductor, so in the event that a wire does touch the casing, it won't conduct.

• Earthing is when an earth wire is added. This conducts unwanted charge to the Earth and away from the component. It is green or green and yellow. If enough charge builds up, it may cause electrons to be pulled through the air and create sparks,which is potentially dangerous. The Earth Wire helps avoid this. In components/devices with metal cases, the Earth Wire touches the case, so if the case conducts, the electrons are taken away to the earth.

• Fuses appear in plugs and are always in series with the live wire. If the current is too high for the component, the fuse will melt and break the circuit (as in there will be a gap) so it no longer functions. It protects the appliance from power surges that could otherwise cause it to be fried by the excess current. Fuses come with different maximum currents (usually 3A, 5A and 13A I think)

• Circuit breakers have an electromagnet that is activated if the current reaches above a certain limit. This pulls an iron switch towards it which opens a switch and breaks the circuit.