OCR Gateway Physics P2

Carson Yeung
Flashcards by Carson Yeung, updated more than 1 year ago More Less
Grace Bennett
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Carson Yeung
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GCSE Physics Flashcards on OCR Gateway Physics P2, created by Carson Yeung on 06/18/2015.

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Question Answer
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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