11) The National Grid

What is the National Grid?

A large system of cables and transformers that connects power stations to consumers in the UK.

How does electricity demand change throughout the day?

Demand increases in the morning, after school/work, and when it gets dark or cold, and during major events.

Why do power stations often run below maximum capacity?

To have spare capacity for unexpected demand spikes or shutdowns of other stations.

What is the benefit of using a high potential difference in the National Grid?

It reduces energy loss due to heating in the wires, making transmission more efficient.

What is the typical potential difference used in the National Grid for transmission?

400,000 V

How does a transformer increase potential difference?

By using more turns on the secondary coil than on the primary coil (step-up transformer).

What happens to current when potential difference is increased in a transformer?

The current decreases.

What is the purpose of a step-down transformer in the National Grid?

To reduce the voltage to safer levels for consumer use.

How is power related to potential difference and current in transformers?

Power = Potential Difference × Current.

What is the power conservation relationship in transformers?

The power in the primary coil equals the power in the secondary coil:

V_primary × I_primary = V_secondary × I_secondary