Highworth Physics - Electricity Generation Questions

Front 1

Which of these statements apply to using biofuels to generate electricity? Select two answers.

A - They can be burnt in power stations in a similar way to fossil fuels.

B - They do not produce any carbon dioxide when they burn.

C - Burning biofuels adds less carbon dioxide to the air overall than burning fossil fuels.

D - Burning biofuels in a power station does not add any carbon dioxide to the air overall.

E - The carbon contained in biofuels was taken out of the atmosphere by respiration when the plants grew.

Back 1

A - They can be burnt in power stations in a similar way to fossil fuels.

C - Burning biofuels adds less carbon dioxide to the air overall than burning fossil fuels.

Front 2

A TV uses 90 W of power when it is switched on. Electricity costs 16.5p per Unit.

(a) What is 90 W in kW?

(b) How much energy (in kWh) does the TV use in six hours?

(c) How much does this electricity cost?

(d) Why should you switch a TV off when it is not being used, instead of putting it on standby?

Back 2

(a) 0.09 kW

(b) 0.54 kWh

(c) 8.91 p

(d) The TV still uses electricity on standby.

Front 3

(a) State two disadvantages of using energy from uranium to generate electricity.

(b) State two advantages of using uranium.

Back 3

(a) Any two from: takes a long time to start up the power station, an accident in a nuclear power plant can be dangerous, they are expensive to decommission, and nuclear waste stays radioactive for thousands of years and needs to be stored.

(b) Any two from: energy is available at any time, nuclear fuel/uranium is cheap compared with coal, and a nuclear power station does not emit carbon dioxide or other polluting gases.

Front 4

(a) What is a TV pick-up?

(b) Why do power engineers need to use weather forecasts?

(c) Which kind of power station can start generating in the shortest time if there is an increase in demand?

Back 4

(a) A TV pick-up is a sudden increase in the demand for electricity at the end of a popular TV programme or during an advert break caused by lots of people switching on kettles and other appliances at the same time.

(b) They need to predict how much electricity will be needed, so they can make sure enough power stations are running.

(c) Hydroelectric.

Front 5

State one energy resource that matches each of these descriptions.

(a) Available at any time.

(b)Produces carbon dioxide.

(c) Availability depends on the weather.

(d) Available at predictable times, but not all the time.

Back 5

(a) Any one from: coal, oil, gas, nuclear, biomass, hydroelectricity, or geothermal energy.

(b) Any from coal, oil, gas, or biomass.

(c)Any from solar, wind, or waves.

(d) Tides.

Front 6

Figures 1 and 2 use two types of chart to show the different energy resources used to generate electricity in the UK in three separate years.

What information does Figure 2 provide that Figure 1 does not? The total amount of energy used each year.

Back 6

The total amount of energy used each year.

Front 7

Describe three changes between the energy resources used in 1980 and in 2000.

Suggest reasons for these changes.

Back 7

Any three from: more energy used in 2000, less coal used, gas used in 2000 but not in 1980, proportion/total amount of nuclear increased between 1980 and 2000, and imports used in 2000 but not in 1980.

Reasons given must match the responses in part b. More energy is being used because there are more people in the country, and more and different types of electrical appliance for us to buy and use. Gas-fired power stations are more efficient than coal-fired ones, so the amount of coal being used is decreasing. Imported electricity is needed because the increased use of electricity means we cannot produce enough of our own.

Front 8

Eilean Dubh is a small island off the coast of Scotland, with no mains electricity supply. There are only a few houses on the island,and their total energy use averages 30 000 kWh per year. The islanders currently use a diesel generator to provide their electricity. This costs 20p for every kilowatt hour of electricity generated. They are considering investing in a renewable source of energy. Some details about two alternative energy sources are shown in the table.

(a) What is the maximum possible output of the wind turbine over one year in kWh?

(b) The wind turbines are likely to produce only about one-third of this amount. Why is this?

Back 8

(a) Maximum energy output = power × time =6  kW × (365 × 24) h = 52 560  kWh.

(b) The turbine does not generate electricity if the wind speed is too low, and has to be stopped if the wind speed is too high(either or both of these points for, so it will not generate electricity all the time.

Front 9

(c) If the solar cells generate about 7000 kWh per year, and last for 20 years, how much will each Unit of electricity cost?

(d) The electricity from the wind turbine is likely to cost about 13p per unit. Other than cost, suggest what advantage the wind turbine has over the solar cells.

Back 9

(c) Total amount of electricity generated = 7000 kWh × 20 years = 140 000 kWh. Cost per Unit = cost of turbine/Units generated =£40 000/140 000 kWh = £0.285, or 28.5  p.

(d) It may be able to generate electricity at night, when the solar cells cannot.

Front 10

(e) If the islanders could get all their electricity from the wind turbine, what would be the payback time for installing the turbine?

Back 10

(e) For each kWh generated the islanders save £0.20, so in a year they save £6000.

Payback time therefore = 4 years 2 months.

Front 11

(a) Give two reasons why using a microwave oven instead of a conventional oven can help to reduce the amount of energy used.

(b) How can homeowners make sure they buy the most efficient appliances?

Back 11

(a) A microwave oven uses less power when it is switched on (1 mark), and it cooks food more quickly so it does not have to be switched on for long.

(b) Check the efficiency labels of all appliances.

Front 12

A ready meal takes an hour to cook in a 3kW conventional oven. The same meal can be cooked in 15 minutes in a microwave oven. The oven uses 850 W to cook food.

(a) Electricity costs 14p per unit. How much does it cost to cook the meal in the conventional oven?

(b) How much money does a homeowner save ifhe uses the microwave oven to cook thesame meal?

(c)Acheap microwave oven costs £50. The homeowner has meals like this about twice aweek. What is the payback time for the microwave oven?

Back 12

(a) Cost= power (kW) × time (h) × cost (p/kWh) = 3 kW × 1 × 14p (1 mark) = 42p

(b) Cost of using microwave = 0.85 kW × 0.25 h ×14p = 2.975p (1 mark) Saving = 39.025p.

(c) No.of meals to break even = £50/£0.39 = 128.2. At 2 meals/week this is 64 weeks

Front 13

Here are some opinions about hydroelectricity.

A Hydroelectric power stations do not contribute to global warming.

B Hydroelectric power stations are useful because they can start and stop quickly.

C Pumped storage power stations can store electricity.

(i) Suggest why most people would think that statement A is correct.

(ii) Explain why it is not quite correct.

Back 13

(i) They do not emit any gases from burning fuels.

(ii) Vegetation rotting when the reservoir is first flooded can emit gases.

Front 14

Here are some opinions about hydroelectricity.

A Hydroelectric power stations do not contribute to global warming.

B Hydroelectric power stations are useful because they can start and stop quickly.

C Pumped storage power stations can store electricity.

(i) How does the start-up time of a hydroelectric power station compare with that of a gas-fired and a coal-fired power station?

(ii) Why is it useful to have some power stations that can start up quickly?

Back 14

(i) It is much faster.

(ii) There are often sudden demands for electricity which cannot be met by increasing the electricity generated by fossil fuel or nuclear power stations.

Front 15

Describe two differences between a pumped storage power station and a normal hydroelectric power station.

Back 15

The pumped storage power station has two reservoirs but a normal hydroelectric power station has only one. The pumped storage power station can move water up or down, the normal one only allows water to flow down.

Front 16

In what form is energy stored in a hydroelectric power station?

At what time of day is a pumped storage power station usually storing energy? Explain your answer.

Back 16

Gravitational potential energy.

During the night.

As this is when demand for electricity is lowest.

But fossil-fuelled/nuclear power stations are still generating because it is not economical to reduce their output. it would take too long to start them up again if some were shut down.

Front 17

Pumped storage power stations can store electricity.

Explain why this statement is not correct.

Back 17

Electricity is not stored; instead, it is used to do something such as pump water uphill. The water can then be released later to flow downhill and generate more electricity, though not all the electricity originally used will be regenerated.

Front 18

(a) What does a transformer do?

(b) Explain the difference between a step-up and a step- down transformer.

(c) What is the National Grid?

Back 18

(a) Changes the voltage of an electricity supply.

(b) Step-up transformers increase the voltage, step-down transformers reduce it.

(c) The system of transmission lines and transformers that distributes electricity around the UK.

Front 19

Explain why the National Grid is needed,instead of just connecting each town only to its nearest power station.

Why is electricity transmitted around the country at very high voltages?

Back 19

Many power stations are in remote places and can produce more energy than needed by their local town. Demand can change in different areas so the National Grid allows almost any power station to supply electricity to any partof the UK.

Less energy is wasted as heat.

Front 20

It costs £9000 to install a set of solar cells in the roof of a house. The suppliers of the solar cells say that the owners should be able to sell approximately £630 of electricity to the grid each year. What is the payback time for the solar cells?

Back 20

9000/630 = 14 years and 4 months.

Front 21

Renewable energy resources can have environmental effects. Give one possible environmental effect of each of the following resources.

(a) Hydroelectricity.

(b) Wind power.

(c) Tidal power.

(d) Biofuels.

Back 21

(a) Any one from: Floods habitats; gases can be emitted as flooded vegetation rots; spoils the view.

(b) Any one from: May kill birds; access roads etc. can disturb habitats; spoil the view.

(c) Any one from: Changes pattern of tidal flow in estuary; may affect wildlife dependent on mud flats; barrage may affect fish migration.

(d) Any one from: There is usually a net emission of carbon dioxide; growing crops for biofuels may involve cutting down forests.

Front 22

Many people think that biofuels do not add carbon dioxide to the atmosphere.

(a) Explain why they think this.

(b) Explain why this idea is not usually correct.

Back 22

(a) The crops grown to produce biofuels take in carbon dioxide from the atmosphere and the same amount is released when the crops are burnt.

(b) Any three from the following: Energy is needed to produce biofuels, to transport them and for fertiliser. This energy is usually obtained from burning fossil fuels, which adds carbon dioxide to the atmosphere.

Front 23

Carbon dioxide and sulphur dioxide can both be emitted when fossil fuels are burnt.

(a) Name one environmental effect of each of these pollutants.

(b) Describe how the emissions of these pollutants can be reduced.

Back 23

(a) Carbon dioxide is contributing to climate change/global warming; sulphur dioxide causes acid rain.

(b) Carbon dioxide can be reduced by capturing and storing the gas, sulphur dioxide can be reduced by removing sulphur from fuels/removing sulphur dioxide from the waste gases in power stations.

Front 24

Most people who own gardens use a powered mower to cut their lawns.

(a) Suggest two advantages of a petrol-engined mower compared to a mower with an electric motor.

(b) Suggest two disadvantages.

Back 24

(a) It does not need a cable or a heavy battery, so can be moved further more easily;there is no safety risk of a cable that could be run over.

(b) Fuel has to be bought from a petrol station and carried back; unpleasant fumes are released.