P5 - Mains Electricity

Question 1

P5 - What does a step-up transformer do?

Answer 1

Increases voltage at power station end.

Reduces current

This stops the transmission cables getting too hot.

Less energy wasted.

More efficient energy transfer.

Question 2

P5 - What does a step-down transformer do?

Answer 2

Decreases the voltage at consumer end of national grid.

Increases the current.

This makes it safer for people to use.

Suitable level for household appliances.

Question 3

P5 - What are the characteristics of mains electricity?

Answer 3

Alternating current

Frequency of 50 Hz

Voltage of 230 V

Question 4

P5 - What do each of the three wires in a plug do?

Answer 4

BROWN - the live wire. This carries the current.

GREEN/YELLOW - the earth wire. This is a safety feature designed to prevent electric shocks.

BLUE - the neutral wire. This is kept at a zero voltage. It completes the circuit

Question 5

P5 - What is meant by the half-life of a radioactive substance?

Answer 5

The time it takes for the radioactivity of a substance to fall to half of its original level.