The National Grid

Energy resources are renewable or non-renewable.

Which two of the following energy resources are renewable?

Tick (✓) two boxes.

Biofuel

Coal

Nuclear

Oil

Wind

Figure 5 shows wind turbines in the countryside.

What are two effects on the environment of using wind turbines to generate electricity?

Tick (✓) two boxes.

Some birds are killed by wind turbines.

There is no fuel cost when using wind turbines.

Wind is an unreliable energy resource.

Wind turbines generate lots of electricity in windy conditions.

Wind turbines produce low frequency noise.

Figure 6 shows a wind turbine.

The useful power output of the generator in the wind turbine is 144 000 W.

The efficiency of the wind turbine is 0.30

Calculate the total power input to the wind turbine.

Use the equation:

Use the Physics Equations Sheet to answer Questions 05.4 and 05.5.

Which equation links current, potential difference and power?

Tick (✓) one box.

power = potential difference × current

The power output of the generator in the wind turbine is 144 000 W.

The potential difference across the generator is 960 V.

Calculate the current in the generator.

Figure 7 shows how the National Grid links the wind turbine to consumers.

The step-up transformer increases the potential difference and decreases the current.

What effect does decreasing the current have on the energy loss from the power cables?

Tick (✓) one box.

The energy loss decreases.

The energy loss is not affected.

The energy loss increases.

What is the function of the step-down transformer in Figure 7 ?

Tick (✓) one box.

To decrease the current.

To decrease the potential difference.

To decrease the power input.

Figure 3 shows how the National Grid links a nuclear power station to consumers.

Explain why step-up transformers are used in the National Grid.

Explain why step-down transformers are used in the National Grid.

Figure 4 shows a transformer.

The potential difference across the primary coil is 345 kV.

The potential difference across the secondary coil is 230 V.

The current in the primary coil is 0.060 A.

Calculate the current in the secondary coil.

Use the Physics Equations Sheet.

Nuclear power stations and coal power stations have an environmental impact.

Compare the environmental impact of generating electricity using these two types of power station.

Figure 10 shows a step-down transformer that is part of a circuit inside a computer.

The transformer connects the mains supply to the computer circuit.

The potential difference across the primary coil is 230 V.

The potential difference across the secondary coil is 48.0 V.

The current in the primary coil is 2.40 A.

Calculate the current in the secondary coil.

Use the Physics Equations sheet.

The current in the primary coil is 2.40 A.

Calculate the time taken for a charge of 288 C to flow past a point in the primary coil.

Use the Physics Equations Sheet.

Give your answer in minutes.

Figure 11 shows the mains electricity circuit for the transformer.

An electrician replaced a faulty switch connecting the transformer to the mains supply.

The circuit was disconnected from the mains supply to prevent the electrician from receiving an electric shock.

Explain why the electrician could have received a shock if the circuit was connected.

Table 2 shows information about the effects of different electrical supplies on the human body.

ac is alternating current.

dc is direct current.

The mains electricity supply in the UK is ac with a frequency of 50 Hz.

Describe why it would be better if the UK mains supply was not 50 Hz ac.

Figure 3 shows how a power station supplies electricity to consumers.

The National Grid is a system of cables and transformers linking power stations to consumers.

Complete the sentences.

Choose answers from the box.

Each answer may be used once, more than once or not at all.

The step-up transformer causes the potential difference to increase and

the current to.

The use of the step-up transformer causes the energy transferred by heating

of the cables to.

The step-down transformer causes the potential difference to decrease and

the current to.

A nuclear power station has a power output of 350 000 000 W

Calculate the energy transferred by the power station in 60 seconds.

Use the equation:

energy transferred = power × time

Table 1 shows some of the waste products produced by three different types of power station.

Which type of power station contributes least to global warming?

Give a reason for your answer.

Which type of power station produces waste products that cause acid rain?

Give a reason for your answer.

Figure 9 shows how the National Grid connects power stations to consumers.

Explain how transformers are used in the National Grid.

A gas-fired power station has a power output of 50 MW

Calculate the energy transferred during 24 hours.

Table 5 shows some of the waste products produced by three different types of power station.

Evaluate the environmental impact of the power stations in Table 5.

An energy input of 1.3 × 10¹⁸ J is supplied each year by power stations to the National Grid.

Not all of this energy is supplied to consumers. Some of the energy is wasted in the distribution process.

Write the equation which links efficiency, total input energy transfer and useful output energy transfer.

The energy supplied each year to consumers is 1.2 × 10¹⁸ J

Calculate the efficiency of the distribution process.

How is electrical power transmitted across the National Grid to make the process as efficient as possible?

Tick one box.

Write the equation which links energy transferred, power and time.

A wind turbine supplies a power output of 8000 kW for 1200 seconds.

Calculate the energy transferred by the wind turbine in kJ

Describe the environmental advantages and disadvantages of using wind turbines to generate electricity in the UK.