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Birds don't get electrocuted when they stand on pylon wires - why not?

Electricity - The National Grid

How does electricity travel from power stations to your home safely and efficiently? This GCSE Physics quiz explores the National Grid and transformer voltage changes.

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Fascinating Fact:

Before electricity reaches homes and businesses, step down transformers reduce the voltage to safer levels, such as 230 V for domestic use in the UK.

In GCSE Physics, you learn how the National Grid links power stations to homes and industry. High voltages are used to transmit electricity efficiently over long distances, then transformers reduce the voltage to a safe level for everyday appliances. Understanding how step up and step down transformers work helps you explain why the system is both efficient and safe.

Key Terms

National Grid: The network of cables and transformers that carries electricity from power stations to homes and businesses.
Transformer: A device that changes the potential difference of an alternating current supply, either increasing or decreasing it.
Step down transformer: A transformer that reduces the output voltage to a lower, safer value for local use.

Frequently Asked Questions (Click to see answers)

What is the National Grid in GCSE Physics?

The National Grid is the system of power stations, cables and transformers that delivers electrical energy from where it is generated to homes, schools, hospitals and businesses across the country.

Why is a high voltage used in the National Grid?

A high voltage is used so that the current can be kept low, which reduces energy losses as heat in the transmission lines. This makes long distance electricity transfer more efficient.

How do transformers work in the National Grid?

Transformers in the National Grid change the voltage of alternating current. Step up transformers increase voltage for transmission, while step down transformers reduce it again near homes and local areas.

Try These Related Quizzes

1 .

What is transferred through the National Grid?

Coal

Petrol

Gas

Electricity

The highest voltage cables are made from aluminium which is light, strong and a good electrical conductor

2 .

What voltage is used to transfer electricity through the National Grid?

Up to 300,000 V

Up to 400,000 V

Up to 500,000 V

Up to 600,000 V

There are 132 kV, 275 kV and 400 kV circuits that make up the grid

3 .

How is such a high voltage produced?

By using step-up transformers

By using step-down transformers

By using a Darlington pair

None of the above

Step-up transformers can be used to increase voltage whilst decreasing current, conserving the total amount of energy

4 .

Why is a high voltage used?

It increases the amount of energy wasted in cables

It reduces the amount of energy wasted in cables

The cables cannot transfer low voltage electricity

So they can transfer the electricity at a high current

Some electricity used in homes and businesses on the south coast could have been generated in Scotland so keeping energy losses down to the minimum possible is really important

5 .

What is the mains voltage in homes in the UK?

120 V

170 V

230 V

270 V

Whilst in the UK the voltage is 230 V, in other countries this can vary, for example, in the USA it is 110 V

6 .

How is voltage from the National Grid changed into 230 V for home use?

Step-up transformer

A thin cable

A thick cable

Step-down transformer

Step-down refers to the voltage

7 .

Electricity is sent through the National Grid using which type of electrical current?

Alternating current

Direct current

Alternating and direct current

Neither alternating nor direct current

If it was sent using DC, it would not be possible to use transformers so a lot more energy would be wasted (or we would need to use extremely high and therefore more dangerous voltages)

8 .

What voltage is produced in power stations?

15,000 V

20,000 V

25,000 V

30,000 V

This then needs to be increased for distribution via the National Grid

9 .

Why don't birds get electrocuted when they stand on pylon wires?

As they are not connected to any grounded point, the electricity will not flow through the bird and will continue through the cables

They do get electrocuted

Birds do not conduct electricity

None of the above

Electricity will always try to make its way back to the Earth by finding the most efficient path. Air is actually a good electrical insulator and high voltages are required for electricity to be able to pass through it. The birds are not earthed and surrounded by air, so the electricity follows the line of least resistance - the wire

10 .

Why does reducing the current and increasing the voltage mean less energy is lost?

A high voltage means they can transfer the electricity at a high current, transferring it at a high current means fewer electrons travelling through the cables which reduces the amount of collisions between electrons and the cables, thus wasting less energy as heat

A high voltage means they can transfer the electricity at a low current, transferring it at a low current means fewer electrons travelling through the cables which reduces the amount of collisions between electrons and the cables, thus wasting less energy as heat

A high voltage means they can transfer the electricity at a low current, transferring it at a low current means more electrons travelling through the cables which reduces the amount of collisions between electrons and the cables, thus wasting less energy as heat

A high voltage means they can transfer the electricity at a low current, transferring it at a low current means fewer electrons travelling through the cables which increases the amount of collisions between electrons and the cables, thus wasting less energy as heat

The heating effect of an electric current increases in direct proportion to the square of the current, so keeping the current as low as possible saves energy losses

You can find more about this topic by visiting BBC Bitesize - The National Grid and mains electricity

Author: Martin Moore