P2: PLUGS AND THE NATIONAL GRID

Question 1

What is the colour and function of the live wire?

Answer 1

-brown
-provides alternating pd at 230V from mains supply

Question 2

What is the colour and function of the neutral wire?

Answer 2

-blue
-completes circuit

Question 3

What is the colour and function of the earth wire?

Answer 3

-green and yellow striped
-safety feature: prevents appliance casing from becoming live by creating a path for current to flow to the ground

Question 4

Why is plastic casing used on plugs?

Answer 4

-insulator

Question 5

Why are brass pins used in plugs?

Answer 5

-good conductor of electricity
-doesn’t rust

Question 6

Why are copper wires used?

Answer 6

-good conductor of electricity
-malleble

Question 7

How do circuit breakers work?

Answer 7

-measure difference in current in live and neutral wires
-if the difference is too great an electromagnetic switch ‘trips’ which stops the flow of current

Question 8

What is the national grid?

Answer 8

the national grid distributes electricity across the country from the power station to the consumer

Question 9

What is the role of the step-up transformer in the national grid?

Answer 9

-step-up transformers increase voltage and decrease current (voltage is increased from about 25,000V to 400,00 V causing the current to decrease) to reduce energy being transferred to the surroundings as heat

Question 10

What is the role of the step-down transformer in the national grid?

Answer 10

-step-down transformers increase current and decrease voltage to 230V so its safe to use in appliances