1. Electrical Faults Open Circuit
Current cannot flow as there is a gap in the circuit.
The lamp is off.
Open circuit faults have a higher resistance than expected.
break in wire
No Fault
Open Circuit

2. Short Circuit
Current flows from one wire to the other not reaching the lamp.
The lamp is off.
Short circuit faults have a lower resistance than expected.
Electrical current will always try and follow the path of least resistance.
wires touching
No Fault
Short Circuit

3. The Continuity Tester
The continuity tester is a circuit that is used to detect open
circuit faults.
If the wire is ok the circuit is complete and the lamp lights.
If there is an open circuit fault there is a gap in the circuit and the lamp is off.

4. Extension Leads Extension blocks are connected in parallel.
Care must be taken when using an extension block to connect appliances to a socket.
The more appliances connected in parallel the bigger the current flowing through the flex to the extension block.
5 A
2 A
3 A
?? A
to socket
This could cause the flex to overheat.