10.4 Mains Electricity

Figure 1 shows an incomplete table of the insulating cable colours for the wires in a UK plug.

Complete the table by filling in the missing information.

An electric lamp contains a 3 A fuse.

Explain the role of the fuse within the circuit of the lamp.

Which of the diagrams shows a fuse which has been correctly connected to the circuit?

A	B
C	D

A battery-powered lawn mower uses direct current.

Which graph correctly shows direct current?

A	B
C	D

Electric lawnmowers are powered by the mains supply. An electric lawnmower is fitted with a 5 A fuse. 

Which row of the table correctly describes where the fuse should be fitted and how the fuse does its job?

 

	Where is it positioned?	What does it do?
A	live wire	reduces the current to 5 A
B	neutral wire	breaks the circuit
C	live wire	breaks the circuit
D	neutral wire	reduces the current to 5 A

The owner of an electric lawnmower wants to install a circuit breaker to protect themself and the lawnmower from a surge in current.

Under normal operating conditions, the lawnmower draws a current of 4 A.

The manufacturer provides the graph shown in Figure 1 with the purchase of the circuit breaker.

Figure 1

Which row of the table correctly describes what will happen when the current is 4 A, and what will happen if the current rises to 14 A?

 

	4 A	14 A
A	circuit does not break	circuit does not break
B	circuit does not break	circuit breaks quickly
C	circuit breaks quickly	circuit does not break
D	circuit breaks quickly	circuit breaks quickly

Sam has a toaster and the fuse blows. Sam takes the fuse out and sees that it has 13 A written on it.

Sam doesn't have any 13 A fuses, but they have a 3 A fuse and decide to use that.

Describe what will happen when Sam switches on the toaster.

Sam buys a 13 A fuse for the toaster.

Figure 1 shows the possible positions to place the fuse in the circuit.

Figure 1

Which fuses show the correct position for the fuse?

   A   Fuse X and Fuse Y

   B   Fuse X only

   C   Fuse Z only

   D   Fuse X and Fuse Z

As well as a fuse, the toaster is fitted with an earth wire as a safety feature.

Explain how the earth wire makes the toaster safe to use.

Which of the following shows an A.C. circuit?

Which graph correctly shows an alternating current?

Figure 1 shows a circuit diagram for a D.C. circuit. The circuit contains a fuse.

Figure 1

Each of the ammeters reads 1.2 A.

Which option correctly describes the fuse that should be fitted to the circuit in this position?

   A   1.0 A

   B   3.0 A

   C   5.0 A

   D   13.0 A