GCSE Physics revision

The National Grid

Energy transfers

AQA 4.2.4.3

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AQA student objectives

Learning pathway

ALL 🎯

Explain why the National Grid system is an efficient way to transfer energy.

MOST 🎯🎯

Apply the scientific explanation of the national grid to a relevant example.

SOME 🎯🎯🎯

Analyse a new situation involving the national grid and explain the scientific reasoning.

Revision summary

Read on screen, then print for Cornell-style active revision.

When transporting electricity across the country, there is a huge risk of energy waste because the power levels involved are extremely high.
The National Grid uses transformers to keep electrical energy transfers as efficient as possible, minimising energy loss during transmission.

A step-up transformer increases the voltage of the electricity as it leaves the power station.
Boosting the voltage to a very high level causes the current to become very low, which reduces energy lost as heat in the transmission cables.
Despite the change in voltage and current, the power remains the same throughout the transmission process.

2. Step-Up TransformersAQA

A step-up transformer increases the voltage of the electricity as it leaves the power station.
Boosting the voltage to a very high level causes the current to become very low, which reduces energy lost as heat in the transmission cables.
Despite the change in voltage and current, the power remains the same throughout the transmission process.

A step-down transformer decreases the voltage once the electricity reaches homes and other buildings, making it safe for everyday use.
In a step-down transformer, the number of turns on the primary coil is greater than on the secondary coil, causing the voltage to fall.
You should be able to recognise and label both step-up and step-down transformers on a National Grid diagram in your exam.

3. Step-Down TransformersAQA

A step-down transformer decreases the voltage once the electricity reaches homes and other buildings, making it safe for everyday use.
In a step-down transformer, the number of turns on the primary coil is greater than on the secondary coil, causing the voltage to fall.
You should be able to recognise and label both step-up and step-down transformers on a National Grid diagram in your exam.

Electromagnetic induction is the principle that a changing electric current can induce a magnetic field, and a changing magnetic field can induce an electric current.
Transformers rely on electromagnetic induction to change the voltage of a circuit.
An alternating current (AC) passing through the primary coil creates a continuously changing magnetic field in the iron core.
This changing magnetic field induces a new alternating current in the secondary coil, which is wrapped around the same iron core.

4. Electromagnetic InductionAQA

Electromagnetic induction is the principle that a changing electric current can induce a magnetic field, and a changing magnetic field can induce an electric current.
Transformers rely on electromagnetic induction to change the voltage of a circuit.
An alternating current (AC) passing through the primary coil creates a continuously changing magnetic field in the iron core.
This changing magnetic field induces a new alternating current in the secondary coil, which is wrapped around the same iron core.

A transformer consists of two coils of wire — a primary coil and a secondary coil — both wrapped around a shared iron core.
The iron core links the two coils, allowing the changing magnetic field produced by the primary coil to pass through to the secondary coil.
The voltage is only induced when an alternating current is used, as a steady direct current would not produce a changing magnetic field.

5. Structure of a TransformerAQA

A transformer consists of two coils of wire — a primary coil and a secondary coil — both wrapped around a shared iron core.
The iron core links the two coils, allowing the changing magnetic field produced by the primary coil to pass through to the secondary coil.
The voltage is only induced when an alternating current is used, as a steady direct current would not produce a changing magnetic field.

The ratio of voltages across the primary and secondary coils depends on the ratio of the number of turns on each coil.
This relationship is expressed as: V_p / V_s = N_p / N_s where V_p and V_s are the primary and secondary voltages, and N_p and N_s are the number of turns on each coil.
In a step-up transformer, the secondary coil has more turns than the primary coil, so the output voltage is higher than the input voltage.

6. The Transformer EquationAQA

The ratio of voltages across the primary and secondary coils depends on the ratio of the number of turns on each coil.
This relationship is expressed as: V_p / V_s = N_p / N_s where V_p and V_s are the primary and secondary voltages, and N_p and N_s are the number of turns on each coil.
In a step-up transformer, the secondary coil has more turns than the primary coil, so the output voltage is higher than the input voltage.

Electricity generated at a power station first passes through a step-up transformer, which greatly increases the voltage for efficient long-distance transmission.
Once the electricity reaches local areas, a step-down transformer reduces the voltage to a safe level suitable for use in homes and businesses.
This two-stage transformer system makes the National Grid an efficient and safe method of distributing electrical energy across the country.

7. The National Grid: The Full PictureAQA

Electricity generated at a power station first passes through a step-up transformer, which greatly increases the voltage for efficient long-distance transmission.
Once the electricity reaches local areas, a step-down transformer reduces the voltage to a safe level suitable for use in homes and businesses.
This two-stage transformer system makes the National Grid an efficient and safe method of distributing electrical energy across the country.