Mains Electricity

Question 1

in the UK, what is used to connect electrical appliances to the mains supply?

Answer 1

electrical appliances in the UK are normally connected to the main supply using the three-core cable

Question 2

there are 3 wires in a three core cable

what are they called

Answer 2

Live wire- the brown wire
Neutral wire - the blue wire
Earth wire - the green/yellow striped wire

Question 3

what are the wires in the 3 core cable made of?

what is beneficial about this?

Answer 3

copper
copper is a good conductor of electricity

the coating is made of plastic
plastic is not a good conductor of electricity

Question 4

what is the function of the live wire?

what is the live wire connected to?

Answer 4

Carries the alternating potential difference from the supply (electricity generators)
(approx 230V)

the live wire is connected to a fuse in the plug.

Question 5

what is the function of the blue wire?

Answer 5

completes the circuit. PD =0V compared to the live wire

Question 6

what is the function of the Earth wire?

Answer 6

This is a safety wire to stop the appliances from becoming live

Question 7

In a circuit, label the parts and the functions

Answer 7

• A live wire carries 230V of electricity from generators
• the live wire is attached to the fuse
• energy is transferred in appliance
• the neutral wire completes the circuit

                                              live- carries 230V 
                                              electricity from
                                              generators
                              \_\_\_\_\_\_\_\_\_
                             |              |    ——————— ~ —————————— |                                |\_\_fuse\_\_|                 | |                                                                •| |   energy is transferred in appliance      |• |               \_\_\_\_\_\_\_\_\_\_\_\_                               | ———— |appliance |—————————

• • • • • • |___________|

earth wire

Question 8

what is the symbol for a fuse?

Answer 8

________
| |
———————
|________|

like a resistor but with a line through it

Question 9

what are some hazardous things to notice?

Answer 9

The live wire is extremely dangerous and could easily be fatal if touched
even possible when the switch is opened
this is because the first part of the live wire running to the switch, still has a pd of 230V

Question 10

Even when the switch is open, why can the live wire be just as fatal if touched?

Answer 10

because the first part of the live wire running to the switch still has a PD of 230V

Question 11

what is the PD of the earth

Answer 11

0V

Question 12

what would happen if someone touched a live wire while standing on the ground/earth?

Answer 12

a current would flow through the person into the earth and they’d be electrocuted

Question 13

why can appliances with a metal case be very dangerous?

Answer 13

if the live wire comes loose and touches the metal case, the case can become live and get the pd of 230V (because the metal is a conductor of electricity)

that could give someone a fatal electric shock if they touch the live case

Question 14

what is the metal case attached to ?
how are they connected?
what happens if the case becomes live in this case?
how does this help with safety

Answer 14

the earth wire
they are connected into the ground with a metal rod
if the case becomes live, a huge current flows to the earth.
the fuse melts and shuts off the current.
This PREVENTS anyone from getting electric shock from touching the case