P2.5 Mains electricity

Question 1

What is the difference between direct and alternating current?

Answer 1

direct current is in one direction only

alternating current repeatedly reverses its directions

Question 2

What do we use for mains electricity?

Answer 2

alternating current

Question 3

How do we measure alternating current?

Answer 3

to measure frequency of an a.c. supply we measure the time period of the waves then use the formula:
frequency = 1 / time taken for 1 cycle

Question 4

What are sockets and plugs made of and why?

Answer 4

stiff plastic materials that enclose the electrical connections, plastic is used because it is a good electrical insulator

Question 5

What are electrical wires made of?

Answer 5

copper because its a good conductor insulated by an outer layer of flexible plastic

Question 6

What does a 3-pin plug consist of?

Answer 6

a live wire - brown
a neutral wire - blue
an earth wire-green and yellow

Question 7

What is a fuse and how does it work?

Answer 7

contains a thin wire that heats up, melts, and cuts off the current if the current is too large
always fitted
in series with the live wire

Question 8

What is a circuit breaker and how does it work?

Answer 8

an electromagnetic switch that opens (“trips”) and cuts off the current if too much current passes through the circuit breaker