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91 Cards in this Set
- Front
- Back
Adv of photocells (4) |
- are robust, don't need maintained - don't need fuel and no long power cables - no pollution caused = doesn't increase global warming - renewable source |
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Disadvantage of photocells |
Don't produce electricity when it's too dark or cloudy |
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A photocell contains two pieces of silicon joined together to make a ...? |
P-n junction |
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The n piece in P-n junction thats made by joining two silicones in photocell is what? |
An impurity added to produce an excess of free electrons |
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The P type silicon which is made by photocell when adding two silicones together to make P-n junction is what? |
Has a different impurity than n type silicon added to produce an absence of free electrons |
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Sunligit contains energy packets called... |
Photons |
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Photons cause what? |
Free electrons to move producing an electric current |
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The output from a photocell depends on what three things ? |
* light intensity * surface area exposes * distance from light source |
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The sun is very hot and produces infrared radiation with a very short wavelength. Because of this the glass is.... to this short wavelength radiation Fill in... . |
Glass is transparent to this short wavelength radiation |
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The sun is very hot and produces infrared radiation with a very short wavelength. What do walls and floor inside a building do with that radiation? |
Absorb the radiation, warm unless nd reradiate infrared radiation |
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The walls and floors are not as hot as the sun and this affects the infrared radiation...how? |
The wavelength radiated is longer |
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When the infrared radiation is radiated by floors and walls causing it to have longer wavelength, what happens when it tries to go via glass? |
Glass reflects the longer radiation back inside the building |
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Why are solar reflectors moved by computer? |
To ensure they always face the sun |
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Remember |
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Adv of wind turbines? |
Don't contribute to global warming as doesn't produce pollution |
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Wind turbines disadvs (3)? |
Take a lot of space. Spoil the view Noisy |
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The current from a dynamo can be increased by what three things? |
* using stronger magnet * increasing number if turns on the coil *.rotating the magnet faster |
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The output from a dynamo can be display on an....? |
Oscilloscope |
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What does oscilloscope trace show? |
How current produced by the dynamo varies with time |
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The time for one complete cycle is called..? |
The period of the alternating current |
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A simple generator consists of what? |
Coil of wire rotating between the poles of a magnet. |
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Remember |
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Power station How does the process go to generate electricity? |
Water boils or burn fossil fuels to boil water to produce steam Steam at high pressure will turn the turbine The turbine drives the generator |
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Tip |
Most wavelengths of electromagnetic radiation can pass via the earths atmosphere but infrared radiation is absorbed |
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Carbon dioxide occurs naturally in the atmosphere as a result of what 5 things? |
•…• natural forest fires •…• volcanic eruptions •…• decay of dead plant and animal matter •…•.it's escape from the oceans •…• respiration |
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Man made carbon dioxide is caused by... (4) |
Burning fossil fuels Waste incineration Deforestation Cement manufacture |
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Water vapour is the most significant greenhouse gas because.... |
Almost all water vapour occurs naturally A mere 0.001% comes from human activity |
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How is methane produced (naturally and usual way)? |
When organic matter decomposes in an environment lacking oxygen |
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Natural sources where methane is produced? |
Wetlands, termites and oceans |
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Man made sources of methane being produced? (4) |
Cattle, rice paddies, burning fossil fuels and burying waste in landfill |
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How do greenhouse cause global warming? |
When radiation from sun goes to earth, it is absorbed by and warms the earth. The earth then reradiates the energy as infrared radiation with a longer wavelength. This longer wavelength radiation is absorbed by the greenhouse gases which warms the atmosphere = global warming |
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What causes global cooling? |
Dust in the atmosphere |
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Global warming. How do factories contribute to it? |
Smoke from factories reflect radiation from the town back to earth |
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Global cooling. How does ash cloud from volcano contribute to it? |
Reflects radiation from sun back into space |
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Why is electricity cheaper at night? |
Because less is needed during might but it still has to be produced |
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The choice of energy sources depends on what 4 factors? |
Availability, ease of extraction, effect of the environment, associated risks |
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Why do national grids have transformers to step up voltage as high as 400,000 V? |
The high voltage leads to... * reduced energy loss * reduced distribution costs * cheaper electricity for consumers |
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If atom has same number of electrons and protons, they are...? |
Neutral |
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Ionisation involves gaining or losing electrons. When atoms gain electron, it becomes.... |
Negatively charged |
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Ionisation involves gaining or losing electrons. When atoms lose electrons, they become... |
Positively charged |
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Formation of ions can cause chemical reaction that could lead to...? |
Changing molecules behaviour E.g. make DNA production of proteins to change |
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What are the radiations that come from the nucleus? |
Beta, alpha, gamma |
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Which radiation out of three causes most ionisation? |
Alpha |
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Which radiation out of the three causes the least ionisation? |
Gamma |
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What stops alpha? |
Easily absorbed by a sheet of paper |
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Whats stops gamma? |
Thick lead |
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Which out of three radiations is most penetrating? |
Gamma |
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What stops beta from penetrating? |
Few millimetres of aluminium |
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Experiments can be done to identify each type of radiation from it's penetrating power (gamma, alpha and beta) but what should be taken into account? |
Background radiation |
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Example of where alpha radiation is used. |
Smoke alarms |
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How do smoke alarms work with alpha radiation? |
Radiation ionises the oxygen and nitrogen atoms in air causing small electric current occurring. When smoke rises it stops atoms from being ionised, making the alarm receive less current = goes off |
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Example of where beta radiation is used |
Paper rolling mill |
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Tip |
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Example of where gamma radiation is used? |
Kill bacteria and treat cancer or finding leakage in pipes |
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Passage of blood and other substances can be traced around the body using what radiation? |
Beta or gamma |
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What is plutonium? |
Waste product from nuclear reactors which can be used to make nuclear bombs |
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Plutonium can be used to make what? |
Nuclear bombs |
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What waste does nuclear reactor produce? |
Plutonium |
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How to get rid of low level radioactive waste? |
Bury in landfill sites |
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How to get rid of high radioactive waste? |
Encase it in glass then buried deep underground |
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Remember |
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Advs in using nuclear power stations? |
No greenhouse gases are made Doesn't use fossil fuels |
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Disadvantages in using nuclear power stations? |
High maintenance Costs are high Risky |
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What are comets? |
Comets are balls of ice and dust in orbit around the Sun |
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What is meteor made up of? |
Grains of dust that burn up as they pass via earths atmosphere. |
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How do meteors form a tail? |
They heat the air (hydrogen) round then which glows = shooting star |
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Why can't we see black holes? |
Because light can't escape it and it's mass is large while size of it is small |
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Advs of unmanned probes over humans |
Can go to places where conditions are dealt to humans Cost less No life threatened
No sources needed for it (e.g. food) |
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Outside spacecraft, humans need to wear special spacesuits. What do they use for eyes? |
Dark visor that stops him or her from getting blind |
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The suit that astronauts wear is... |
Pressurised and has supply of oxygen |
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Disadv of unmanned spacecraft ? |
They have to be very reliable because there's no way to repair them if they break down |
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Remember! |
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What are asteroids? |
Mini planets - rocks that we're meant to form a planet |
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Whats asteroid belt? |
Gravity between Mars and Jupiter |
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Most orbits are where? |
Between mars and Jupiter |
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Just so you know... |
Asteroids are large rocks that were left over from the formation of the solar system |
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How did all planets form? |
When clouds of gas and dust collapsed together due to gravitational forces of attraction |
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What stopped asteroids forming a planet? |
Theory; Jupiter's gravitational force (asteroid belt) |
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Theory of how moon formed |
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Tip |
as the comet passes close to the sun, the ice melts and solar winds blow the dust into the comets tail which always points away from the sun. |
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What is a object called when it is near earth? |
NEO |
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Just so you know... |
Speed of a comet increases as it approaches the sun and decreases as it gets further away. This is because of the changing gravitational attraction. |
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The expanding universe |
Almost all of the galaxies are moving away from each other with the further galaxies moving fastest |
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Galileo observer four moons orbiting Jupiter. This confirmed that not everything orbited the earth and supporter Copernicus's idea that planets orbit the sun. Why people were against this idea? |
Religious: earth was at the centre!! |
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Why is the universe constantly expanding? |
As a result of big bang |
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When a source of light is moving away from an observer, its wavelength appears to be what for us? |
Longer |
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When source of light moves away from us, it appears to have longer wavelength which causes its light that we see to become red. This is called? |
Red shift |
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How do scientist exploit red shifts? |
By this info (red shift) they can workout the age of the universe |
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Life cycle of a star (small star) |
1. Protostar 2. Normal life (star) 3. Red giant star 4. White dwarf 5. Black dwarf |
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Life cycle of a star (big star) |
1. Nebula 2. Normal life (star) 3. Red super giant star 4. Supernova 5. If big enough = black hole or IF not big enough = neutron star |
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Why do small stars shine longer than big stars? |
Because although they have less hydrogen , they use it at smaller rate so in bigger stars hydrogen gets used up faster |