Dangers of electricity

Question 1

Common hazards of electricity

Answer 1

Damaged insulation - If someone touches an exposed piece of wire, they could be subjected to an electric shock

Overheating of cables - Passing too much current through too small a wire can lead to the wire overheating. This could cause a fire or melt the insulation, exposing live wires

Damp conditions - If moisture comes into contact with live wires the moisture could conduct electricity either causing a short circuit within a device or posing an electrocution risk

Question 2

What is a fuse

Answer 2

A safety device designed to cut off the flow of electricity to an appliance if the current becomes too large

It is a glass cylinder which contains a thin metal wire

Question 3

How does a fuse work

Answer 3

If the current in the wire becomes too large the wire heats up and melts which causes the wire to break, breaking the circuit and stopping the current.

Question 4

What are the typical fuse sizes

Answer 4

3A, 5A and 13A

Question 5

How do you chose the correct fuse

Answer 5

It needs to be the next size up,

e.g. for a 3A appliance a 5A resistor is advised

Question 6

What is earthing

Answer 6

many electrical appliances have metal cases

This poses a potential safety hazard as if a live wire comes into contact with the case there is an electrocution danger

So an earth wire is an additional safety wire that can reduce this risk

Question 7

How does earthing work

Answer 7

The earth wire provides a low resistance path to the earth

This causes a surge of current in the earth wire and hence in the live wire

The high current through the fuse causes it to melt and break

This cuts off the supply of electricity to the appliance making it safe