domestic uses and safety

Question 1

in mains electricity an ac or dc supply, what do they stand for

Answer 1

ac supply
ac- alternating current
dc- direct current

Question 2

define ac and dc

Answer 2

ac- current that changes direction at a specific frequency
dc- one directional current flow

Question 3

what is the frequency and voltage of the UK mains electricity supply

Answer 3

frequency - 50Hz
voltage - 230V

Question 4

how many wires are in cables connecting electrical appliances to mains. name the wires

Answer 4

1. live wire
2. neutral wire
3. earth wire

Question 5

insulation colour used on earth wire

Answer 5

green and yellow stripes

Question 6

insulation colour used on live wire

Answer 6

brown

Question 8

insulation colour used on neutral wire

Answer 8

blue

Question 9

explain when the earth wire does and doesn’t carry a current

Answer 9

1. under normal circumstances, no current flows through the earth wire
2. if a fault occurs in the appliance (casing becomes live) , current will flow to ground

Question 10

what potential is neutral wire at

Answer 10

0V

Question 11

state the pd between the live and earth wires

Answer 11

230V

Question 12

purpose of neutral wire

Answer 12

complete circuit by connecting appliance back to mains supply

Question 13

for metal appliances where is the earth wire connected to

Answer 13

1. earth wire is connected to the metal casing of appliance
2. if live wire becomes loose and touches the casing, the current will flow through the earth wire, preventing electrocution