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When the National Grid was established, the cables were all carried by pylons.

Physics - The National Grid (AQA)

Discover how the National Grid moves electricity across the country, matches supply to demand and keeps voltage and frequency stable for homes, schools and businesses.

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Fascinating Fact:

If demand rises suddenly the frequency dips. Rapid response from batteries, gas turbines and hydro helps stabilise it.

In GCSE Science Physics, you study how the National Grid transfers electricity efficiently from power stations to homes and businesses. You also learn how operators control voltage, current and frequency to keep supply safe and reliable.

Key Terms

National Grid: The high-voltage network of cables and substations that carries electricity around the country.
Frequency: The number of cycles of alternating current per second, measured in hertz, kept close to 50 Hz in the UK.
Rapid-response generation: Power sources that can start quickly, such as gas turbines, batteries or pumped storage hydro.

Frequently Asked Questions (Click to see answers)

What is the National Grid in GCSE Physics?

The National Grid is the linked system of power stations, transformers and high-voltage transmission lines that delivers electricity from generators to homes, schools and other users.

Why is grid frequency kept close to 50 Hz?

Grid frequency is kept near 50 Hz so that generators stay in sync and devices like motors, clocks and transformers work correctly and safely without being damaged.

How does the National Grid balance electricity supply and demand?

Control centres monitor demand and adjust power station output, use rapid-response sources and sometimes ask large users to reduce use so that supply and demand stay matched.

Try These Related Quizzes

1 .

Where would you find a step-down transformer?

Near to the power station

In an electricity substation near to the consumers

Part way along the power cables of the National Grid

In people's homes

They are used to reduce the high voltages of the National Grid ready to distribute to consumers

2 .

About seven to eight percent of the electrical energy is lost in the National Grid, mainly as which type of energy?

Thermal energy

Light energy

Sound energy

Kinetic energy

When electricity passes through any wire there is a slight resistance. This causes some of the electrical energy to be transferred into heat energy

3 .

Why is electricity carried by the supergrid at very high voltage?

It is a legal requirement

That is the voltage that power station generators produce

It wastes less energy

At lower voltages, it would not have the power to go all over the country

The higher voltages mean lower currents are flowing so less energy is wasted

4 .

The National Grid is a system of what?

A system of cables

A system of cables and transformers

A system of cables, transformers and power stations

A system of cables, transformers, power stations and consumers

The transformers change the voltage of the electricity in the National Grid. Power stations and consumers are at either end of the National Grid but not parts of it

5 .

Which of the following would be a good stand-by power station?

Coal fired power station

Pumped storage hydroelectric power station

Wind turbines

All of the above

You need a power station with a very short start up time that will definitely be available at times of peak electricity demand

6 .

Why are CHP (combined heat and power) stations more efficient than most fossil fuel burning power stations?

They use the heat to heat local buildings as well as to generate electricity

They are more modern

They are a lot smaller

They are run by local businesses so they have to be more efficient to make them more profit

The electricity from CHP stations is usually used locally too. This also makes them more efficient as it avoids the inevitable losses caused by transporting electricity for hundreds of miles

7 .

The electricity generated at power stations is usually at 25,000 V. Which type of transformer is used to change the voltage required by the supergrid?

Step-in

Step-out

Step-up

Step-down

You can remember this because the voltage is increased from the power station to the National Grid (it is 'stepped up')

8 .

Which of the following contains the missing words from the passage in the correct order?

________ transformers are used at power stations to produce the very high ____________ needed to ensure that electricity is transmitted efficiently through the National Grid. Such high voltages are dangerous to use in the home, so _________ transformers are used in substations near to homes to reduce the voltage to safe levels. The voltage of ________ electricity is about 230 V.

Step-up, voltages, step-down, household

Large, current, small, safe

Step-up, current, step-down, safe

Step-down, voltages, step-up, factory

If you associate step-up transformers with power stations, that narrows your choice to two possibilities

9 .

Which of the following is not an advantage of the National Grid?

Electricity is available at a standard voltage throughout Britain

If a power station breaks down, others can increase output to compensate

It makes electricity much cheaper

Sudden increased demands in electricity can be met

The grid is about having a reliable system that can cope with sudden demands or power station breakdowns without consumers having a power cut. Having a National Grid does not make electricity costs any cheaper

10 .

When the National Grid was established, the cables were all carried by pylons. Now, some of the cables of the supergrid have been buried underground. Which of the following is not an advantage of buried high voltage cables?

Underground cables lose less energy

Underground cables are less likely to be damaged or broken in bad weather

Underground cables are more expensive to install

Underground cables have lower maintenance costs

Some people believe that living near overhead power cables causes health issues because of the electromagnetic fields they emit. Underground cables do not emit electromagnetic fields

You can find more about this topic by visiting BBC Bitesize - Mains electricity and alternating current - AQA

Author: Kev Woodward (PGCE, Science & Chemistry Teacher, Quiz Writer)