Energy resources and efficiency

விளையாடிக் கற்றுக்கொள்ளுங்கள்

ஆற்றல் சம்பாதிக்க இந்த கேள்விகளுக்குப் பதிலளியுங்கள், பின்னர் மீன் பிடித்து ஆராயுங்கள். கணக்கு தேவையில்லை.

கல்வியாளர்களுக்கு: Energy resources and efficiency (MYP Physics, Year 2)-க்கான தயாரான பாட ஸ்லைடுகள், திருப்புதல் குறிப்புகள் — உங்கள் பாடத்தில் அவற்றைப் பயன்படுத்தவும், அல்லது கற்பவர்கள் நேரலை விளையாட்டாக விளையாடும் ஊடாடும் வகுப்பு செயல்பாடாக தலைப்பை இயக்கவும்.

பாட குறிப்புகள்

Big idea: choosing where our energy comes from

Big idea. Key concept: Systems. An energy resource, a power station and the homes it supplies form one connected system, so a change in one part affects all the others.
Related concept: Consequences. Every way of making electricity has benefits and costs for people and for the environment.
Global context: Globalization and sustainability. We share one planet, so how a country makes its electricity affects the climate and the resources everyone depends on.
An energy resource is a source we can use to heat buildings, move vehicles and make electricity.
Non-renewable resources will run out because we use them much faster than they form. Coal, oil and natural gas (the fossil fuels) and uranium are non-renewable.
Renewable resources are replaced as fast as we use them, or cannot run out. Wind, solar, hydroelectric, geothermal, tidal, wave and biofuels are renewable.
Most of our resources trace back to the Sun: fossil fuels formed from living things that once used sunlight, and the Sun heating the air drives the wind. Nuclear, geothermal and tidal energy do not.

Renewable and non-renewable energy resources

Fossil fuels and the power station

Coal, oil and natural gas formed over millions of years from the remains of plants and tiny animals that were buried and squashed under rock. We are using them far faster than they form.
In a power station the boiler burns the fuel. Energy moves from the chemical store of the fuel to the thermal store of the water, which turns to steam.
The steam rushes through a turbine and spins it, so energy is now in the kinetic store of the turbine.
The turbine turns a generator, which transfers energy electrically. The electricity passes through a transformer and along power lines to homes and businesses.
A condenser cools the used steam back into water so that it can be heated again.
Burning fossil fuels releases carbon dioxide, a greenhouse gas that adds to global warming. Coal and oil also release sulfur dioxide, which dissolves in rain to make acid rain.
On the plus side, fossil fuel stations are reliable: they can be switched on whenever people need electricity, whatever the weather.

Parts of a coal-fired power station

Nuclear power

In a nuclear reactor, the nuclei of uranium atoms are split when a neutron hits them. This is nuclear fission.
Each splitting releases energy and more neutrons, which can split further nuclei. This is a chain reaction. Control rods soak up neutrons to keep the reaction steady.
The energy heats water into steam. After that, the turbine and generator work just as they do in a fossil fuel station.
A reactor releases no carbon dioxide while it runs, and a small mass of fuel releases a very large amount of energy. Output is reliable day and night.
The drawbacks are radioactive waste, which must be stored safely for a very long time, the high cost of building and later closing a station, and the serious (though rare) consequences of an accident.
Uranium is mined from the ground and the supply is limited, so nuclear power is non-renewable even though it does not burn fuel.

Nuclear fission of a uranium nucleus

Renewable resources

Wind: moving air turns the blades of a wind turbine, which spins a generator. No fuel is burned, but the wind must be blowing.
Solar: solar cells transfer energy from light directly to electricity. Solar panels can also heat water. Output falls in cloud and is zero at night.
Hydroelectric: water stored behind a dam has gravitational potential energy. When it falls through a turbine the energy becomes kinetic, then electrical. Building a dam can flood land and affect wildlife.
Geothermal: in volcanic regions, hot rocks heat water underground. The steam turns a turbine. It is reliable, but only possible in certain places.
Tidal and wave: the rise and fall of tides, or the movement of waves, turns turbines. Tides are very predictable but the equipment is costly and can affect marine life.
Biofuels: fuels made from plants or waste. The plants take in carbon dioxide as they grow, so the carbon dioxide released when the fuel burns is partly balanced out. Growing the crops needs land that might be used for food.
Because some renewables depend on the weather, countries usually use a mix of resources and look for ways to store energy.

A hydroelectric power plant

Wasted energy and efficiency

Energy is conserved: it cannot be created or destroyed, only transferred between stores. So the total energy input always equals the useful output plus the wasted output.
Wasted energy usually ends up in the thermal store of the surroundings, spread out and hard to use again. We say it is dissipated.
Efficiency tells us how much of the input is useful: efficiency = useful energy output / total energy input.
Efficiency is a number from 0 to 1, or a percentage from 0% to 100% if you multiply by 100. No real machine reaches 100%.
Worked example. A lamp takes in 200 J and gives out 30 J of light. Efficiency = 30 J / 200 J = 0.15, which is 15%. The wasted energy is 200 J - 30 J = 170 J.
A Sankey diagram shows energy transfers as arrows. The width of each arrow is proportional to the amount of energy. The input arrow splits into a useful arrow and a wasted arrow.
Ways to reduce waste include lubrication to cut friction, insulation to slow thermal losses and better design.

A simple Sankey diagram

Think like a scientist: which blades make the best wind turbine?

Question. Does the length of the blades change how far a model wind turbine can lift a small mass?
The independent variable is the blade length, for example 8 cm, 12 cm and 16 cm. The dependent variable is the height the mass is lifted in 10 seconds, measured in centimetres.
To make it a fair test, keep the same fan, the same fan distance and speed setting, the same mass, the same number of blades and the same blade angle. Use a small battery-powered fan, never mains equipment.
Repeat each blade length three times and calculate the mean, so that one odd reading does not decide the result.
Evaluate a method. A fan may not blow steadily, the height is hard to read while the mass moves, and three blade lengths give only a rough pattern. Suggest how to improve each one.
Inquiry task. Plan an investigation into whether the number of blades changes the height lifted. State the variable you change, the variable you measure, three variables you control and how many repeats you will take.

ஸ்லைடுகள்

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பதிவு செய்க — இலவசம்உள்நுழைக

பயிற்சி கேள்விகள்

இலவச முன்னோட்டம் — 53-இல் 8 கேள்விகள். அனைத்தையும் பார்க்க பதிவு செய்யவும்.

1.Which of these is a renewable energy resource?
Easy
- ACoal
- BWind
- CNatural gas
- DUranium
2.What does it mean to call an energy resource non-renewable?
Easy
- AIt cannot be used to make electricity in any form
- BIt is only available while the Sun is out shining
- CIt always damages the land where it is found now
- DIt will run out as we use it faster than it forms
3.Which fuel formed from the buried remains of ancient plants?
Easy
- ACoal
- BWind
- CUranium
- DTidal water
4.What is the job of the generator in a power station?
Easy
- ATo burn the fuel and make steam for the turbine
- BTo cool the used steam back into liquid water
- CTo turn the turbine's kinetic energy into electricity
- DTo carry the electricity along the high power lines
5.Which gas released when fossil fuels burn adds to global warming?
Easy
- AOxygen
- BNitrogen
- CCarbon dioxide
- DHelium
6.Which renewable resource uses hot rocks underground?
Easy
- AGeothermal
- BTidal
- CSolar
- DHydroelectric
7.What is the useful energy output of a filament lamp?
Easy
- AHeat
- BSound
- CChemical energy
- DLight
8.Which of these is a disadvantage of wind turbines?
Medium
- AThey release carbon dioxide while they are working
- BThey only generate when the wind is blowing hard enough
- CThey use up a fuel that will eventually run out
- DThey leave radioactive waste that must be stored

மேலும் கேள்விகள்

9.Which energy store does water behind a dam have that makes it useful for hydroelectric power?
Easy
- AElastic potential energy
- BGravitational potential energy
- CChemical energy
- DNuclear energy
10.Nuclear power releases no carbon dioxide while a reactor runs. Why is it still called non-renewable?
Medium
- AThe reactor needs coal to start each morning
- BNuclear stations only work during the night time
- CThe reactor gives out huge amounts of carbon dioxide
- DThe uranium fuel is a limited resource that will run out
11.Which statement about solar cells is correct?
Easy
- AThey transfer energy from light directly to electricity
- BThey boil water to make steam that spins a turbine
- CThey produce the same output at night as at noon
- DThey burn a fuel inside the panel to make heat
12.Why do most countries use a mix of energy resources rather than just one?
Medium
- AEvery resource gives exactly the same amount of electricity each day
- BMixing resources together turns fossil fuels into renewable ones
- CEach one suits different times and places, which makes a mix more reliable
- DUsing several resources at once is demanded by a law of physics
13.Which equation correctly gives efficiency?
Easy
- AEfficiency = total energy input / useful energy output
- BEfficiency = wasted energy output / total energy input
- CEfficiency = useful energy output / total energy input
- DEfficiency = useful energy output x total energy input
14.A device has an efficiency of 0.4. What does this mean?
Medium
- A40% of the input energy is transferred usefully
- B40% of the input energy is wasted
- CIt wastes 40 J of energy every second
- DIt is 40 J more efficient than a similar device
15.Why can no real machine be 100% efficient?
Medium
- AMachines destroy a little of the energy every time they are switched on
- BMachines create extra energy that always has to be removed again
- CEfficiency can only be worked out for machines that are renewable
- DSome energy always goes to the thermal store of the surroundings
16.A student says: Energy is used up when a bulb lights, so the total amount of energy goes down. Which reply is best?
Hard
- AShe is right, because the bulb destroys the energy it uses to make light and heat
- BEnergy is conserved: it goes to light and to the thermal store of the surroundings
- CShe is right, but only for old bulbs that work at less than 50% efficiency
- DShe is wrong, because the bulb makes brand new energy whenever it warms up
17.What does the width of an arrow in a Sankey diagram represent?
Easy
- AThe speed of the energy transfer
- BThe amount of energy being transferred
- CThe temperature of the device
- DThe time the transfer takes
18.A student investigates how blade length affects the height a model wind turbine lifts a mass. What is the independent variable?
Easy
- AThe height the mass is lifted
- BThe speed setting of the fan
- CThe mass that is being lifted
- DThe blade length
19.In the same investigation, which pair of things should be kept the same to make it a fair test?
Medium
- AThe fan distance and the fan speed setting
- BThe blade length and the height lifted
- CThe height lifted and the time of day
- DThe blade length and the student who reads the ruler
20.A student tests three turbines once each and decides that the 12 cm blades are best. What is the biggest weakness in the method?
Hard
- AShe measured the lifted height in centimetres rather than metres
- BShe tested more than two different blade lengths in total
- CEach blade was tested once, so a fluke could look like a pattern
- DShe used a fan that blows in a straight line at the blades
21.An island needs electricity all night. Why are solar panels on their own unsuitable?
Hard
- AThey give out carbon dioxide gas whenever it is dark
- BThey need coal burning nearby before they can start up
- COutput is zero at night, so storage or a back-up is needed
- DSolar energy is a non-renewable resource that will run out
22.Coal and oil also release sulfur dioxide when they burn. What problem does this gas help to cause?
Easy
- AAcid rain
- BRadioactive contamination
- CTidal flooding
- DA loss of gravity
23.Which of these are renewable energy resources? (select all that apply)
Medium
- ACoal
- BWind
- CNatural gas
- DTidal
- EGeothermal
24.Which of these are advantages of nuclear power stations? (select all that apply)
Medium
- AA small mass of fuel releases a lot of energy
- BThe waste stays dangerous for a very long time
- CThey release no carbon dioxide while running
- DUranium is a renewable resource
- EThey can run reliably day and night
25.Which actions would reduce the energy wasted by a machine? (select all that apply)
Hard
- ARoughening the surfaces that rub together
- BOiling the moving parts
- CRedesigning it to waste less energy
- DInsulating the parts that get hot
- ELeaving it running when it is not needed
26.A solar panel produces more electricity in bright sunshine than in thick cloud.
Easy
True or false?
27.Coal is renewable because new coal forms every year.
Easy
True or false?
28.Every real machine wastes some energy, so none is 100% efficient.
Medium
True or false?
29.Wasted energy is destroyed.
Easy
True or false?
30.The carbon dioxide released when biofuel burns was taken in by the plants as they grew.
Medium
True or false?
31.A device that wastes 30 J of every 100 J of input has an efficiency of 30%.
Hard
True or false?
32.Match each renewable resource to the thing that provides its energy.
Easy
- Wind
- Hydroelectric
- Geothermal
- Biofuel
- Moving air
- Falling water from a dam
- Hot rocks underground
- Plants grown for fuel
33.Match each part of a power station to its job.
Medium
- Boiler
- Turbine
- Generator
- Condenser
- Heats water to make steam
- Is spun by the moving steam
- Transfers energy electrically as it spins
- Cools used steam back into water
34.Match each resource to one of its drawbacks.
Medium
- Coal
- Nuclear
- Solar
- Hydroelectric
- Releases carbon dioxide when burned
- Leaves radioactive waste to store
- Gives no output at night
- Needs a dam that floods land
35.Put the energy transfers in a coal-fired power station in the correct order.
Medium
- Kinetic energy of the spinning turbine
- Chemical energy in the coal
- Electrical energy from the generator
- Thermal energy heats water to steam
36.Put these steps in order to show how a wind turbine makes electricity.
Easy
- Electricity flows to the grid
- The blades turn the shaft
- Wind pushes on the blades
- The generator spins
37.A lamp takes in 200 J of electrical energy and gives out 30 J as light. Using efficiency = useful energy output / total energy input, what is its efficiency as a percentage?
Easy
38.An electric motor takes in 500 J and lifts a load, transferring 350 J usefully. What is its efficiency as a percentage?
Medium
39.A machine takes in 400 J of energy and has an efficiency of 60%. How much energy does it waste, in joules?
Medium
40.A device has an efficiency of 30% and must give 150 J of useful output. How much energy must be put in, in joules?
Hard
41.A kettle element transfers 1350 J to the water for every 1500 J of electrical energy supplied. What is the efficiency of the kettle as a percentage?
Easy
42.For every 5000 kJ of chemical energy in the coal it burns, a power station delivers 1750 kJ of electrical energy. What is its efficiency as a percentage?
Hard
43.Falling water in a hydroelectric station transfers 1000 J of kinetic energy to the turbine, and the generator gives out 800 J of electrical energy. What is the efficiency as a percentage?
Medium
44.A machine takes in 600 J and wastes 420 J as thermal energy. Work out the useful output, then the efficiency of the machine as a percentage.
Hard
45.A 60 W filament lamp is switched on for 30 s. Energy transferred = power x time. If the lamp is 5% efficient, how much energy does it transfer as light, in joules?
Hard
46.Four devices each take in energy and give out some useful energy. Put them in order from least efficient to most efficient.
Hard
- Device Q: 45 J useful from 90 J
- Device P: 12 J useful from 80 J
- Device S: 36 J useful from 40 J
- Device R: 30 J useful from 120 J
47.Complete the sentence about fuels.
Easy
Coal, oil and natural gas are known as ____ fuels.
48.Complete the definition of efficiency.
Medium
Efficiency is the useful energy ____ divided by the total energy ____.
49.Complete the sentence about renewable power.
Medium
Wind turbines and solar panels burn no fuel, so they release no ____ while they generate electricity.
50.Describe one advantage and one disadvantage of using wind power to generate electricity.
Medium
51.Explain why a coal-fired power station is not 100% efficient. Say where the wasted energy goes.
Hard
52.A country is deciding whether to replace a coal-fired power station with a nuclear one. Give one argument for and one argument against the change.
Hard
53.In 2019, a pie chart of world primary energy use gave these approximate shares: oil 33%, coal 27%, natural gas 24%, nuclear 4%, renewables 12%. About what percentage came from fossil fuels?
Medium
- A60%
- B76%
- C96%
- D84%

திருப்புதல் குறிப்புகள்

## Energy resources and efficiency - **Non-renewable** resources (coal, oil, gas, uranium) will run out; **renewable** resources (wind, solar, hydroelectric, geothermal, tidal, wave, biofuels) are replaced. - A power station chain is: fuel, boiler, steam, **turbine**, **generator**, electricity. - Burning fossil fuels releases **carbon dioxide** and (coal and oil) sulfur dioxide. - Nuclear power releases no carbon dioxide while running, but leaves **radioactive waste**. - Wind and solar depend on the weather, so countries use a **mix** of resources. - Energy is **conserved**: input = useful output + wasted output. - **Efficiency = useful energy output / total energy input.** Multiply by 100 for a percentage. - In a Sankey diagram the **width** of an arrow shows the amount of energy.

Energy resource: A source of energy we can use for heating, transport and making electricity.
Renewable: Replaced as fast as it is used, or cannot run out, such as wind, solar and tidal power.
Non-renewable: Will run out because it is used faster than it forms, such as coal, oil, gas and uranium.
Fossil fuel: Coal, oil or natural gas, formed over millions of years from the remains of living things.
Turbine: A set of blades that is spun by steam, wind or moving water.
Generator: A device that is turned by a turbine and transfers energy electrically.
Nuclear fission: The splitting of a large nucleus, such as uranium, which releases energy.
Hydroelectric: Electricity made by water falling from a height through a turbine.
Geothermal: Energy from hot rocks underground, used to make steam.
Biofuel: A fuel made from plants or waste.
Conservation of energy: Energy cannot be created or destroyed, only transferred between stores.
Dissipated energy: Wasted energy that has spread out into the surroundings and cannot easily be used again.
Efficiency: Useful energy output divided by total energy input, as a fraction or percentage.
Sankey diagram: A diagram whose arrow widths show how much energy goes to each output.

ஃப்ளாஷ் கார்டுகள்

What is a non-renewable resource?

One that will run out because it is used faster than it forms.

Name the three fossil fuels.

Coal, oil and natural gas.

Which gas from burning fossil fuels adds to global warming?

Carbon dioxide.

What does a turbine do in a power station?

It is spun by steam (or wind or water) and turns the generator.

What does a generator do?

It transfers the kinetic energy of the turbine to electrical energy.

What is nuclear fission?

The splitting of a large nucleus, such as uranium, which releases energy.

Why is nuclear power non-renewable?

Its uranium fuel is limited and cannot be replaced.

Give one disadvantage of nuclear power.

It leaves radioactive waste that must be stored safely for a very long time.

Why is wind power not always reliable?

The turbines only generate when the wind is blowing hard enough.

What store has water held behind a dam?

Gravitational potential energy.

What does conservation of energy mean?

Energy is never created or destroyed, only transferred between stores.

Where does most wasted energy end up?

In the thermal store of the surroundings, where it is dissipated.

Write the efficiency equation.

Efficiency = useful energy output / total energy input.

A device takes in 200 J and gives 50 J of useful output. What is its efficiency?

25%, because 50 / 200 = 0.25.

What does the width of a Sankey arrow show?

The amount of energy in that transfer.

Name two ways to reduce wasted energy.

Lubricate moving parts to cut friction, and insulate to cut thermal losses.

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இந்த தலைப்பிற்கான ஒவ்வொரு கேள்வியையும், ஸ்லைடுகளையும், ஃப்ளாஷ் கார்டுகளையும் மற்றும் திருப்புதல் குறிப்புகளையும் பார்க்க இலவச கணக்கை உருவாக்கவும்.

பதிவு செய்க — இலவசம்உள்நுழைக

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இந்த தலைப்பிற்கான முந்தைய தேர்வு பயிற்சி விரைவில் வருகிறது.

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