P2 - The National Grid

What is the National Grid?

A system of transformers and high-voltage cables that transfers electricity from power stations to homes and businesses

What does the National Grid connect?

It connects power stations to homes, schools, factories, etc.

Is a power station part of the National Grid?

No, only the cables and transformers are part of the National Grid

Why is energy lost when transmitting electricity?

Because of resistance in the wires, which causes thermal energy loss

How can energy loss in transmission cables be reduced?

By increasing the potential difference using a step-up transformer

What is the role of a step-up transformer?

To increase the potential difference before electricity is transmitted through power lines

Why do we increase the potential difference in the National Grid?

Because a higher potential difference means lower current, which reduces energy loss

Why is it important to say "less energy is lost" instead of "less electricity is lost" in exams?

Because electricity is not lost, only energy is lost due to resistance — saying "less electricity is lost" is incorrect

What is the role of high-voltage cables in the National Grid?

They transmit electricity across long distances with reduced energy loss

What is the role of a step-down transformer?

To decrease the potential difference to a safe level (around 230 V) before it enters homes

What potential difference is electricity transmitted at after passing through a step-up transformer?

Several hundred thousand volts (e.g. 400,000 V)

What potential difference is electricity reduced to before entering homes?

Around 230 volts

Why can't high voltage be passed directly into homes?

Because it would be dangerous and could damage appliances

What is the main advantage of using high potential difference for transmission?

It reduces energy loss in the form of heat in the wires

What is the current like in the transmission cables when voltage is high?

The current is low, which reduces heating and energy loss

What does a transformer do?

It changes the potential difference of electricity

What type of current do transformers work with?

Alternating current (AC)

Why don't people want to live near power stations?

Because they are noisy, polluting, and considered undesirable (so power stations are usually built far from homes)

What are the two main types of transformers in the National Grid?

Step-up transformers and step-down transformers

How does the National Grid balance safety and efficiency?

By using high voltages to reduce energy loss and step-down transformers to make it safe for home use