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Karteikarten von Carson Yeung, aktualisiert more than 1 year ago
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Erstellt von Grace Bennett
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Kopiert von Carson Yeung
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| Frage | Antworten |
| What are the advantages of photocells? | -They are robust and don't need much maintenance. -no fuel or long power cables are needed. -No pollution and they don't contribute to global warming. -they use a renewable energy source resource. |
| How does a photocell work? | -A photocell is made up of two pieces of silicon joined together to make a p-n junction. One piece has an impurity added to produce an excess of free electrons - n-type. Whereas the other piece has a different impurity to give an absence of free electrons p-type. Photons from energy packets form the sun, cause free electrons to move, producing an electric current. |
| What destine output of a photocell depend on? | -Light intensity. -Surface area exposed. -distance from the light source. |
| How can the current from a dynamo be increased? | -Using a stronger magnet. -increasing the number of turns on the coil. -rotating the magnet faster. |
| What does a simple generator consist of? | -Of a coil of wire rotating between the poles of a magnet. -the coil cuts through the magnetic field as it spins. -a current is produced in the coil. |
| How can a current also be produced when the coil does not move? | -Instead the magnets can move. |
| How do conventional power stations produce power? | -Water boils and produces steam. -Steam at a high pressure turns a turbine. -the turbine drives a generator to produce electricity to then be taken to a transformer. |
| How does carbon dioxide naturally occur in the atmosphere? | -natural forest fires. -volcanic eruptions. -decay of dead plants and animals. -respiration. -escaping from the ocean. |
| How is man-made carbon dioxide cause? | -Burning of fossil fuels, waste incineration, deforestation and cement manufacture. |
| What is the most significant greenhouse gas?And why? | -Water vapour: -As almost all water vapour occurs naturally. -0.001% comes from human activity. -Half of the greenhouse effect is due to water vapour and a further quarter is due to clouds. |
| How is methane produced? | -When organic matter decomposes in an environment lacking oxygen: -natural sources consist of wetlands, termites and oceans. -man-made sources consist of the mining and burning of fossil fuel, digestive processes of animals,rice paddies and the burying of waste in landfills. |
| What is the greenhouse effect? | -The electromagnetic radiation from the Sun has a relatively short wavelength. This radiation is absorbed by and warms the Earth |
| What affects does dust have in the atmosphere? | -the smoke from factories reflects radiation from the town back to earth, the temperature rises as a result. -the ash clouds from a volcano reflects radiation from the sun back into space, the temperature falls as a result. |
| Why is electricity cheaper at night? | -Electricity is cheaper at night as it is not needed as much, but still has to be produced. |
| What is the national grid? | -Is a series of transformers and power lines that transport electricity from power stations to consumers. |
| Transformers in the national grid are used to step up the voltage to 400,000V, why is high voltage wanted? | -Reduced energy loss, was a high current leads to heat energy being transferred to the environment. -reduced distribution costs. -cheaper electricity for customers. |
| Atoms are neutral what does this mean? | -They contain the same number of protons and electrons. |
| What does ionisation involve? | -involves gaining or losing electrons: -when the atom gains electrons it becomes negatively charged. -when the atom loses elections it becomes positively charged. |
| What sort of chemical reactions can ion cause? | -such reactions may disrupt the normal behaviour of molecules with the body, e.g. may cause DNA strand to break or change, which is potentially harmful. |
| where does alpha, beta and gamma radiations come from in an atom? | -From the nucleus. |
| Which radiation causes the most ionisation and the least? | -Alpha causes the most ionisation and gamma the least. |
| How do smoke alarms work with a source of alpha radiation? | -the radiation ionises the oxygen and nitrogen atoms in air, causing a very small electric current, which is detected. When smoke fills the detector in the alarm during a fire, the air is not so ionised so there is less current and the alarm sounds. |
| What is gamma radiation used for? | -Gamma radiation kills microbes and bacteria so it is used to sterilise medical instruments. Or for leaks in pipes in drains. |
| What is plutonium? | -Is a waste product from nuclear reactors which can be used to make nuclear bombs. |
| how is radioactive waste dealt with? | -Low level radioactive waste can be buried in landfill sites. -High level is encased in glass and buried deep underground or reprocessed. |
| why is the storage of radioactive waste important? | -As it can remain active for thousands of years, and must be stored well away from any water sources. Plus it could also be a potential target by terrorists to contaminate land or water supplies. |
| What are advantages to nuclear power? | -Fossil fuel reserves aren't depleted and no greenhouse gases are discharged into the atmosphere. -Disadvantages are its very high maintenance and decommissioning costs, and there is a risk of accidents. |
| What sort of orbits do comets have? | -They have elliptical orbits: in which they pass inside the orbit of mercury and go out beyond pluto's orbit. |
| What is a meteor made up of? | -Grains of dust that burn up as they pass through the earth's atmosphere: they heat the air around them which glows and the streak is known as a 'shooting star'. |
| Where are black holes formed? | -Where large stars used to be: -you cannot see them as n light can escape them. -It also has a very large mass but very small size. |
| Why do moons orbit planets, and planets orbit stars? | -Because a centripetal force acts upon them: -centripetal forces act towards the centre of the circular orbit. -Gravitational attraction is the source of the centripetal force. |
| Where do unmanned probes go? | -Where the conditions are deadly for humans. |
| How are spacesuits designed to be able to go into space? | -dark visor stops astronaut from being blinded. -is pressurised and has a supply of oxygen. -surface of suit can withstand temperatures between 120-(-160)℃. |
| At what speed does light travel? | -300 000km/s |
| What are asteroids? | -Mini-planets or planetoids orbiting the sun: -they are large rocks left over from the formation of the solar system. |
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