1. Additional Physics – Forces
Exam Date -
Electrical Safety
L/O :- To understand electrical safety features

2. Quick quiz What are the three different pins in a 3 pin plug?
What colour is the earth wire?
What colour is the neutral wire?
What colour is the live wire?
What wire is the fuse connected to?
What does AC stand for?
What does DC stand for?
What is the frequency of mains electricity?

3. Dangers of Electricity
Timmy
Shocked Bear
Overloading plugs
Exposed wires

4. Electrical faults
An electrical fault could result in a shock, electrocution, resulting in death, or a fire.
A fault occurs when too much current passes through a wire or an appliance.
Come up with examples of things which could result in an electrical fault;
E.g. overloading plugs

5. How can we prevent electric shocks?
Fuses – A fuse contains a thin wire that heats up and melts if too much current passes through it. Different appliances have different fuse ratings. It is always in series with the live wire, between the wire and the appliance.
Circuit Breakers – A circuit breaker is an electromagnet switch that opens when there is a fault. It stops the current in the live wire flowing. They can be reset when the fault has been put right. The advantage over fuses is that they work faster and can be reset more quickly.

6. Residual Current Circuit Breaker – works faster than an ordinary circuit breaker. It cuts off the current in the live wire when it is different from the current in the neutral wire. It is used when there is no earth connection.

7. Watch the demo’s of melting fuse wire and a circuit breaker
Can you now explain in your own words how each one works?

8. Summary
1a) What is the purpose of a fuse in a mains circuit? b) Why is the fuse of an appliance always on the live side? c) What advantages does a circuit breaker have compared with a fuse? 2a) What is the difference between an ordinary circuit breaker and a residual current circuit breaker? b) What are the advantages of an RCCB mains socket compared with an ordinary mains circuit with a fuse in it?

9. What have you learnt?
Can you list the dangers associated with electricity?
Can you explain how a fuse works?
Can you explain how a circuit breaker works?

10. Electricity Revision Questions