The National Grid & Energy Transfers

What is the National Grid?

A network of cables and transformers that transfers electrical energy from power stations to consumers.

Why is electricity transmitted at high potential difference?

To reduce current for the same power transfer, reducing energy losses in cables.

Why does a lower current reduce energy losses?

It reduces heating caused by the resistance of transmission cables.

How is energy wasted in transmission cables?

Electrical energy is transferred to thermal energy stores because of cable resistance.

What is the main advantage of high-voltage transmission?

Less energy is wasted as heat, improving transmission efficiency.

What type of transformer increases the potential difference for transmission?

A step-up transformer.

Where are step-up transformers used in the National Grid?

Near power stations or generating facilities, before long-distance transmission.

What type of transformer reduces the potential difference for consumers?

A step-down transformer.

Where are step-down transformers used?

At substations and near consumers, to provide suitable supply voltages.

Why can't electricity simply be transmitted at low potential difference?

For the same power, a larger current would be needed, causing greater heating losses.

What happens to the current when potential difference is increased for the same power?

The current decreases.

What happens to cable heating when current decreases?

The rate of energy loss through heating decreases.

Why is the resistance of transmission cables important?

It causes energy dissipation when current flows.

How can energy losses in transmission cables be reduced?

Use higher transmission potential differences, lower currents and low-resistance cables.

Why are transformers important to the National Grid?

They allow potential difference to be raised for efficient transmission and lowered for use.

Why does the National Grid use alternating current?

AC can be stepped up and down using transformers.

What is meant by efficient electrical transmission?

Transferring a large proportion of the supplied energy to consumers with minimal losses.

Why is energy conservation important when explaining transformers?

A transformer cannot produce more output energy than the energy supplied.

How do step-up transformers improve transmission efficiency?

They reduce current, which reduces resistive heating losses.

How do step-down transformers make electricity suitable for consumers?

They reduce the high transmission potential difference to appropriate supply levels.