1032567
Description
Flashcards by Melissa Quail, updated more than 1 year ago
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Created by Melissa Quail
almost 10 years ago
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| Question | Answer |
| What does conservation of energy mean? | Energy cannot be created or destroyed, only transformed or transferred. |
| Describe the energy transfer that takes place in a microphone | Electrical energy is converted into sound (useful) and heat (waste) |
| Describe the energy transfer that takes place in a laptop | Chemical energy is transferred to light (useful), sound (useful) and heat (waste) |
| A phone charger has an input energy of 5J. It wastes 1.5J as heat. Draw a Sankey diagram to show this energy transfer. |
Image:
Sankey_diagram (image/png)
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| What is the formula for efficiency? | Efficiency = Useful output power / Total input power |
| What is the definition of power? | The rate of energy transferred |
| What is the formula for power? | Power (W) = energy (J) / time (s) |
| What are Kilowatt hours a unit of? | Energy |
| How do you work out kilowatt hours? | Kwh = kW X hours |
| How do you work out GPE? | Mass x gravity x height |
| Why does a pendulum gradually not swing as high? | Some energy is lost because it is wasted as sound and heat |
| What is the formula for energy? | Energy = power x time |
| How do you work out payback time? | Payback time (years) = cost of insulation / saving each year |
| How do you work out cost effectiveness? | Saving each year/cost of insulation |
| What is a U-value and what does a low U-value tell us? | A U-value is a measurement of the rate of heat loss through a material. The lower the U-value, the better the material is as an insulator. |
| In a power station what happens in the boiler? | Burning coal heats water. The water turns to steam and leaves the boiler. |
| In a power station what happens in the turbine? | Steam turns the turbines. The steam then leaves the turbines and is cooled in huge towers and the water can be recycled. |
| In a power station what happens in the generator? | The turbines drive a large magnet inside a coil. Moving the magnet generates electricity. |
| In a power station what happens in the transformer? | The transformer changes the voltage from 25,000V to 400,000V |
| What is a fuel? | A source of energy |
| What is oil? | Fossils of animals |
| What is coal? | Fossils of plants |
| What are some advantages of wind power? | Clean Renewable source of energy |
| What are some disadvantages of wind power? | Turbines look ugly and are noisy Unreliable |
| Advantages of water power? | Renewable Doesn't affect coastal views |
| What are some disadvantages of water power? | Waves can damage turbines in wave power Tidal power can only be used in places where there is a 5m difference between high and low tide |
| Describe wave power | Waves force the air up and the trapped air turns the turbine which turns the generator. As the wave comes down, the air comes back |
| Describe tidal power | A tidal power station traps each high tide behind a barrage and uses it to turn the generator to make electricity. |
| Describe hydroelectric power | Dam. Dam wall is much thicker at the bottom than the top because the pressure of the water increases with depth. Falling water turns the turbine. |
| Describe geothermal energy | Geothermal energy harnesses thermal energy stored within the Earth. Cold water goes down, gets heated up by radioactive rock, the comes back up as steam and turns the turbine. |
| What causes acid rain? | Sulfur dioxide, produced when sulfur is burned. Sulfur occurs due to impurities in fuels. |
| What does the first step down transformer do? | Reduces voltage from 400,000V to 25,000V |
| What does the second step down transformer do? | Reduces voltage from 25,000V to 230/240V |
| Does a step up transformer have more coils on the output side? | Yes |
| What is the order of start up times for power stations from shortest to longest? | Natural gas, oil, coal, nuclear |
| Energy can be dissipated | True |
| What is a kilowatt hour sometimes called? | A unit |
| Why does voltage need to be increased before electricity goes down power cables? | Increasing the voltage reduces the current required and this reduces the heat energy losses form the cables |
| What is carbon capture? | Carbon capture is the capture of the carbon dioxide released by burning fossil fuels |
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Image:
Nuclear (image/png)
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Image:
Nuclear (image/png)
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| Name two radioactive fuels | Uranium Plutonium |
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