Term
Describe thermal conduction in as much detail as possible. How can you speed up or slow down conduction? |
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Definition
| Thermal conduction occurs when particles collide and energy is transferred between particles. Conduction is only effective in solids because the particles in liquids and gases are too far apart. Metals are excellent conductors because they have free elctrons in the material which can move the heat energy around quickly. Materials with trapped air in them are excellent insulators. |
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Term
| Describe thermal convection in as much detail as possible |
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Definition
| Hot liquids or gases have a lower density because the particles are more spread out. The hot liquid or gas then rise or move upwards. Convection can obviously not happen in solids because the particles cannot move from place to place. |
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Term
| Describe thermal radiation in as much detail as possible. Explain how you can speed up or slow down the emission of heat radiation. |
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Definition
All objects emit (give off) and absorb (take in) heat energy as infra-red radiation or waves. The hotter the object, the more infra red (heat) radiation is emitted. Dull black objects are excellent at both absorbing and emitting infra-red radiation, shiny white objects are the worst at both absorbing and emitting infra-red radiation. The greater the surface area of an object the faster it emits infra red radiation. |
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Term
| What features of a good house prevent heat loss due to conduction? |
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Definition
Double glazing - the trapped air between the glass panes is an excellent insulator Cavity wall insulation - Between the two layers of brick which make up the houses outer wool there is a layer of rock wool which again contains trapped air, an excellent insulator. Loft insulation - again in the loft a layer of insulation (a material with trappped air in it) stops conduction though the roof. |
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Term
| What features of a good house prevent heat loss due to convection? |
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Definition
Doors and windows are kept closed so that air cannot move freely. There are no gaps around the windows or doors again to stop air moving freely. |
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Term
| What features of a good house prevent heat loss due to radiation? |
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Definition
| Paint the walls of the house a shiny pale (white basically) colour rather than dull dark (black) to reduce the emission of infra-red radiation. |
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Term
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Definition
Payback time is the number of years it would take for the savings of a feature to pay for itself. For example, Double glazing a house costs about 5000 pounds. Each year this feature saves you 250 pounds in heating costs. So the payback time would be 20 years (20 years x 250 pounds saving per year = 5000 the cost of buying the double glazing) |
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Term
| Describe the features of a sankey diagram |
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Definition
The width of the arrows is equal to the amount of energy. Useful energy arrows go horizontally across the page. Wasted energy arrows go vertically off the main arrow. |
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Term
| Describe efficiency in as much detail as possible. |
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Definition
Efficiency describes how much energy put into a machine is converted into useful energy. Efficiency = useful energy out / energy in x 100 For example, a typical light bulb needs 100 J of electrical energy every second and only 10 J of that is converted into useful light energy, the rest is wasted thermal energy. The efficiency of a light bulb is therefore only 10%! |
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Term
| What is the national grid |
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Definition
| The national grid is a web of pylons used to distribute electricity around the country. |
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Term
Why is it a bad idea to use large currents to distribute electricity? Why are large currents needed when it gets to the the houses and factories? |
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Definition
Large currents flowing through cables get very hot. So lots of the electrical energy is lost as thermal energy making it very inefficient. When the electrical energy is shared between factories and houses so is the current. Therefore a large current is needed. |
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Term
| What is a step down transformer. Where would you find one and why? |
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Definition
A step down transformer makes the potential difference smaller and the current bigger. The transformer is between the national grid and the houses/factories. The large current is needed because it is shared between all the factories and houses. |
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Term
What is a step up transformer? Where would you find one? What purpose does it serve? |
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Definition
A step up transformer makes the potential difference bigger and the current smaller. You would find a step up transformer between the power station and the national grid. The smaller currents in the cables (the national grid) reduces thermal energy losses. |
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Term
| How does a fossil fuel power station work? |
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Definition
Fossil fuel is burned(chemical energy stored in fuel is converted into thermal energy) Thermal energy is captured by water that turns into moving steam (kinetic energy) The kinetic energy of the steam is captured by a turbine. The turbine passes the kinetic energy to the generator which turns it into electrical energy. |
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Term
What are the advantages of a fossil fuel power station? |
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Definition
Reliable - the power station will always make electricity Produces large amounts of electricity Cheap |
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Term
| What are the disadvantages of a fossil fuel power station? |
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Definition
When you burn the fuel it releases carbon dioxide (responsible for global warming) and sulphur dioxide (acid rain) Energy resource is non renewable so they will run out. |
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Term
| How does shape affect the rate of heat loss? |
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Definition
The greater the surface area the more heat energy that move hot to cold places. Elephants have large ears not to hear better but to cool themselves down faster because of the large surface area. Small animals have a large surface area to a small volume and hence lose heat energy quicker than large animals. |
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Term
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Definition
Power decribes how quickly an object converts energy. Power is measure in Watts. 1 Watt means 1 joule of energy is converted every second. 1 kilowatt (kW) = 1000 Watts (W) |
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Term
What units do we pay for electricity in? How do we work out how much electricity we've used? |
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Definition
We pay for electricity in kilowatthours (kWh) Number of kWh = power of machine x time used in kilowatts in hours To convert watts into kilowatts divide by 1000 |
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Term
| How does a hydroelectric power station work? |
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Definition
Water is stored high up(gravitational potential energy) and then fall through a dam (kinetic energy). The turbine captures the kinetic energy of the falling water. The turbine passes the kinetic energy on to the generator which turns the kinetic energy into electrical energy |
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Term
| What are the advantages of a hydroelectric power station? |
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Definition
Reliable - always produces electricity Does not cause any pollution Renewable energy source - will not run out |
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Term
| What are the disadvantages of a hydroelectric power station? |
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Definition
Requires flooding of large area causing serious damage to ecosystems Only suitable for mountainous areas. |
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Term
| How does a tidal power station work? |
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Definition
Tides push air trapped in large columns through turbines which capture the kinetic energy. The kinetic energy is converted into electrical energy by the generator. |
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Term
| What are the advantages of a tidal power station? |
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Definition
Reliable - will always produce electricity. Renewable so will never run out. Does not cause pollution |
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Term
| What are the disadvantages of a tidal power station? |
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Definition
Damages habitat of local organisms and ecosystems Expensive to build
Has to be built in the mouth of a river. |
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Term
| How does a wave power station work? |
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Definition
Kinetic energy of the waves is captured by the turbines which transfer the energy to generator which turns it into electrical energy. |
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Term
| What are the advantages of a wave power station? |
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Definition
Renewable - will never run out Does not cause pollution |
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Term
| What are the disadvantages of a wave power station? |
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Definition
Not reliable Expensive to build |
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Term
| What are the advantages of a geothermal power station? |
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Definition
Renewable - will never run out Does not cause any pollution Reliable - will always produce electriicty |
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Term
| What are the disadvantages of a geothermal power station? |
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Definition
| Very few suitable sites, usually can only be built in volcanic areas |
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Term
| How does a geothermal power station work? |
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Definition
| Water is pumped underground and heated by radioactive rocks. the kinetic energy of the steam is captured by the turbine and transferred to the generator which converts it into electrical energy |
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Term
| How does a solar power station work? |
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Definition
| Solar cells convert light energy from the Sun onto electrical energy. |
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Term
| What are the advantages of a solar power station? |
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Definition
Renewable - will never run out Does not cause pollution |
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Term
| What are the disadvantages of a solar power station? |
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Definition
Unreliable - not always sunny Very expensive |
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Term
| What are the advantages of a wind power station? |
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Definition
Renewable - will never run out Does not cause pollution |
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Term
| What are the disadvantages of a wind power station? |
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Definition
Not reliable - if it stops being windy then it stops making electricity They are noisy They are ugly |
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Term
| How does a wind power station work? |
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Definition
| The kinetic energy of the moving wind is captured by the turbine which transfers it to the generator which converts it into electrical energy |
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Term
What does renewable energy resources mean? Give examples of renewable energy resources. |
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Definition
Renewable energy is a ource of energy which can be replaced. For example wind when used will soon be replaced. Wind, biomass, solar, geothermal, hydroelectric, wave and tidal are all renewable. |
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Term
What does non-renewable energy resources mean? GIve examples. |
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Definition
Non-renewable means that once used the energy resource cannot be replaced. Once you dig coal up and burn it, it is not replaced by new coal suddenly appearing in the ground to replace it. Coal, oil, natural gas and nuclear fuels like Uranium and Plutonium are non-renewable. |
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