Energy Resources & Power Transmission (OCR GCSE Physics A (Gateway))

The graph shows how the World’s energy use has changed from the year 1971 to the year 2003.

It also shows the amount of different energy sources used.

i) Approximately how much did the total World’s energy use increase from the year 1971 to the year 2003?

Answer = ......................... billion tonnes (oil equivalent)

ii) Which energy source had the greatest use in the year 2003?

iii) The total energy use in the year 2003 was 10.6 billion tonnes (oil equivalent).

Approximately what percentage of this amount was due to fossil fuel use?

Answer = .........................%

Scientists are researching the World’s energy use for the future.

The graph shows some of their research.

i) The future demand for fossil fuels is expected to increase. Give two reasons why scientists are worried about this increase in demand.

1 .....................................................................................................

 2 .....................................................................................................

ii) In the UK the government is closing coal fired power stations and planning for new nuclear power stations to be built.

Suggest why the government wants more nuclear power stations.

Power stations in the UK generate electricity at 25 kV a.c.

The voltage is then increased to 400 kV a.c. and distributed by power lines.

i) Write down the full name of the device used to increase the voltage.

[1]

ii) Why is it important to increase the voltage in these power lines?

[1]

iii) The high voltages across the power lines are reduced to 230 V a.c. for use in the home.

A phone charger changes the 230 V a.c. to a 5 V d.c.

Explain the difference between d.c. and a.c.

[2]

A domestic wind turbine has a power rating which varies from 1.0 kW to 3.0 kW.

i) The domestic wind turbine has an electrical resistance of 23 Ω.

It generates a current of 11 A on a windy day.

Calculate the power output in kW of the turbine on this day.

Answer = ......................... kW [4]

ii) Suggest why the manufacturer gives a range for the power rating of the wind turbine.

[1]

iii) Using just one domestic wind turbine may be an unreliable source of power for a house.

State a reason why.

[1]

Many power stations burn fuels to generate electricity.

Fuels can be renewable or non-renewable.

Wood is used in some power stations.

Why is wood called a renewable fuel?

A student has completed her homework on fuels used in power stations.

Look at her table below.

She has made two mistakes, identify these in the table by putting a cross (x) next to them.

Power stations produce electrical energy and use the National Grid to send the energy to factories and homes in the UK.

A step-up transformer is used in the National Grid.

State what a step-up transformer does.

Domestic UK electrical wiring uses live, neutral and earth wires.

Complete the two empty boxes.

Draw lines to match up the wires to their colour and function.

A teacher uses a power supply in a metal case. The circuit for the power supply includes a fuse.

i) Draw the electrical symbol for a fuse.

[1]

ii) The metal case of the power supply is earthed. A fault occurs and a live wire touches the metal case.

 Explain how earthing the metal case protects the teacher.

[3]

Describe the purpose of each wire used in mains electricity.

Each of the mains electricity wires have different potential difference compared with the human body and consequently present different degrees of danger compared to each other.

i) State the potential difference between each of the wires and the Earth.

[1]

ii) Identify the most dangerous mains electricity wire.

[1]

Describe how someone can receive a lethal electric shock when making contact with the live wire in a mains electricity circuit.

Higher Tier Only

Fig. 1.1 shows a system for transmitting electricity from a power station.

Fig 1.1

State the name of the device used in X and the name of the device used in Y.

Higher Tier Only

Fig. 1.2 shows a transformer connected to an input voltage of 12 V a.c.

Fig. 1.2

i) State the name of a suitable material for the core of the transformer.

[1]

ii) Explain how the diagram in Fig. 1.2 shows a step-up transformer.

[1]

iii) Using the information in Fig. 1.2, calculate the output voltage of the transformer in volts (V).

[3]

Higher Tier Only

Explain why the voltage of the supply to the primary coil of a transformer must be alternating.

Higher Tier Only

A student believes that a step up transformer will produce an output power larger than the input power.

Deduce whether the student is correct.