Mains Plug Wiring: Brown lead Live Blue Lead Neutral Green and Yellow Lead Earth Safety Features: a) the fuse (“blows”) with current overload

Safety Features of the mains plug the fuse “blows” with current overload The earth wire Provides a safe electrical path from the metal case of an appliance The cable grip prevents “mechanical” damage to the electrical components. The moulded plastic case Insulates the connections and firmly separates cables from each other

Electrical Cable consists of three “double insulated” copper leads. This insulation is provided by the OUTER cable made of PVC and the inner plastic “SLEAVES” which are colour coded. The cable itself is made of copper wire which is flexible and has very low resistance. As we will see the most dangerous wire is the brown “Live Wire” The neutral wire is essential to complete the circuit. The earth wire is a safety device which does not carry a current in normal circumstances LIVE WIRE NEUTRAL WIRE EARTH WIRE

The mains a.c. circuit

The mains a.c. circuit

The mains a.c. circuit

The mains a.c. circuit The electric current is pushed back and forth 50 times per second. So the p.d has to change 50 times a second This is done by keeping the neutral lead at 0V and changing the potential applied to the LIVE Wire smoothly from a high positive potential to a high negative potential. The potential difference averages out at 230V

LIVE WIRE +300V p.d./V Time/s -300V p.d./V Time/s NEUTRAL WIRE

Any Appliance With a METAL Case Must Be Earthed Earth connection Metal Case

Case at 230V Metal Case Without Earth Connection Frayed Wire Without an earth connection there will be a high potential difference between the case and earth. The current can move to earth though a person who touches the case Earth at 0V

Frayed Wire Metal Case The large current flowing from live to earth now blows the fuse in the mains plug As soon as the case becomes live current follows the easy route to the ground provided by the earth lead. Large conductor buried in the ground

The Earth Lead This is an earth lead attached to a large copper pipe buried in the ground. Many old electric showers were earthed this way. It is not allowed now because plumbers have started to use plastic pipes.