National Grid (Physics)

What current does the National Grid transmit?

Alternating Current (AC)

What voltage does electricity leave power stations at?

25,000 V

What does a step-up transformer do?

Increases voltage, decreases current

What voltage is electricity stepped up to?

Up to 400,000 V

What does a step-down transformer do?

Decreases voltage, increases current

What is UK domestic mains supply?

230 V, 50 Hz

Why is electricity transmitted at high voltage / low current?

Reduces current → less energy wasted as heat in cables

Formula for power loss in cables?

P = I² × R

What does a transformer NOT change?

Frequency of AC; total power

Step-up transformer coils?

More turns on secondary coil than primary

Step-down transformer coils?

Fewer turns on secondary coil than primary

4-mark exam — Why is the National Grid efficient?

1. Step-up transformer increases voltage / lowers current

2. Lower current means less energy lost as heat (P=I²R)

3. Step-down transformer reduces voltage to safe 230V for homes