Domestic Uses and Safety

Cables, National grids and power

What is mains electricity

An alternating current supply.

What is the frequency and voltage of mains?

F = 50Hz

V = 230V

What is direct current?

Current that only flows in one direction only.

Describe the live wire.

Brown

230V

Dangerous because of its voltage.

Describe the neutral wire.

Blue

0V

Completes the circuit

Describe the earth wire.

Yellow and Green stripes

0V

Stops the appliance from becoming live (electrocutable)

Only carries current if there is a fault (accident in the current) If it does, it carries it to the ground.

What is power?

Energy transferred per second

Write the equation linking power, energy and time

energy = power x time

What is the national grid composed of?

Cables and transformers linking power station to consumers

What is the role of transformers?

It changes the pd

What do step-up transformers do?

Increase the voltage from power stations to the national grid.

(Increasing the voltage decreases the current which means less energy is lost)

What do step-down transformers do?

Decrease the voltage from the national grid to consumers for domestic usage and safety.