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55 Cards in this Set
- Front
- Back
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Advantages+ disadv of photocells? |
Robust, no fuel or cables, no pollution, renewable Do not produce electricity when its too dark or cloudy |
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Explain how a photocell works |
negatively charged electrons are knocked loose from the silicon atoms the electrons flow freely, creating an electric current P has absence of free electrons N has excess of free electrons |
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What does the output of a photocell depend on? |
-Light intensity -Surface area exposed -Distance from light source |
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How does passive solar heating work? |
Short wavelength radiation comes in and is absorbed then reflected as longer wavelength but the windows just reflect it back in. |
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Adv and disadv of wind energy? |
-Don't pollute -Renewable but -noisy -ugly -don't work if it's too windy |
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How can the current be increased in a dynamo? |
More coils Stronger magnet Rotating magnet faster |
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Where can the output of a dynamo be shown? |
Oscilloscope |
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What do you call the time for one complete cycle of wave? |
Period of the alternating current. |
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How does a traditional power station work? |
Water is heated to produce steam. Steam turns the turbine which turns the generator to convert kinetic energy to electrical energy. |
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How does CO2 occur naturally in the air? |
-natural forest fires -volcanic eruptions -decay of dead flora and fauna matter -escape from oceans -respiration |
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How does CO2 occur in the air because of humans? |
-combustion of fossil fuels -waste incineration -deforestation -cement manufacture
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What produces methane? |
-mining -fossil fuels -digestive processes of animals -rice paddies -wetlands -termites |
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Wavelengths of infrared when reaching earth are ____ and leaving are _____ |
short long |
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What do scientists disagree on, on the subject of global warming? |
How much humans have contributed |
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What does choice of energy sources depend on? |
-Availability -Ease of extraction -Effect on the environment -Associated risks |
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What is the national grid? |
A series of powerlines and transformers that transport energy from the power station to the consumer |
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What do transformers do in the national grid? |
Step up voltage as high as 400k volts. This reduces energy loss/distribution costs. They then step it down again to make it suitable for the consumer.
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The greater the current, the hotter the wire, how to transformers combat this? |
Increase the voltage. This lowers the current and means there is less heating effect and therefore less energy lost. |
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Where do alpha beta and gamma rays come from? |
The nucleus |
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Which causes the most ionisation: alpha or gamma? |
Alpha |
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What blocks alpha/beta/gamma? |
Alpha: paper or card Beta: Aluminium Gamma: Lead |
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How to smoke alarms work? |
They send out alpha radiation which ionises the oxygen and nitrogen atoms in the air which causes a tiny electric current. When smoke fills the air, it is not so ionised so the current is less and the alarm sounds. |
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Uses of Beta? |
Thickness testing in a paper mill Track passage of blood and other substances around the body |
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Gamma uses? |
Kill microbes and bacteria Sterilise medical equipment Check for blocks in pipes Track passage of blood and other substances around the body |
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What is plutonium and what is it used for? |
A waste product from nucleur reactors used for bombs. |
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How do we get rid of radioactive waste? |
Low level stuff is buried in landfill sites but worse crap is encased in glass and buried deep underground or reprocessed. |
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Adv and disadv to nucleur power? |
-Fossil fuels aren't used -No greenhouse gasses discharged BUT -High maintenance -Risk of accident -Decommissioning costs are high |
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What kind of orbit do comets have? |
Elliptical. Inside Mercury's orbit and go out beyond Pluto (who ain't a planet officially but always in my heart) |
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What is a meteor made of? |
Grains of dust that burns up as it passes through the atmosphere (shooting star, huh?) |
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What is a black hole? |
Formed where stars used to be LARGE mass but small size |
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What causes orbit? |
Centripetal forces from gravitational attraction. |
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What are the benefits of unmanned probes? |
Can go where us puny humans cannot Don't have to carry food, water, oxygen, etc Cost less No humans at risk |
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What are the different parts of a spacesuit and what are they for? |
Visor stop astronaut being blinded Suit is pressurised and has oxygen for breathing Surface can reach 120 degrees of -160 degrees. |
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How fast does light travel? |
300,000 km/s |
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How long does it take for the sun's light to reach us vs our nearest star? |
8 minutes from sun 4.22 years from the star |
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America plans a manned mission to Mars when? |
After 2020 for $400 billion. |
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What are asteroids? |
Large rocks left over from the formation of the solar system Mini planets orbiting the sun (mostly between Mars and Jupiter) |
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How were all bodies in space formed? |
The collapse of dust and gas due to gravitational forces of attraction. |
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What determines an object's gravitational force? |
Its mass |
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How was the moon formed? |
A result of a collision between planets in the same orbit. Iron core of the other planet joined together with the Earth's core, less dense rocks began orbit around it and joined together to form the moon! |
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What scientific evidence supports our theory of the moon's creation? |
-Average density of the earth is 5500 kg/m3 but moon is only 3300 -No iron on the moon -Moon has the same oxygen composition as earth but rocks on Mars have different |
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What evidence do we have of meteor collisions with earth? |
-Near to a crater they found metal iridium, not usually found on earth but often on meteors -below the layer of iridium there were fossils but few above it -tsunamis have disturbed fossil layers and carried some fragments 300km inland |
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Where do comets orbit? |
Inside the orbit of Mercury and out beyond Pluto |
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How do we stop the thig |
explosions |
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What happens as a comet passes by the sun? |
Ice melts and solar winds blow dust into the comet's tail (that always points away from the sun.) |
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What happens to a comet's speed as it approaches the sun? |
Its speed increases and as it goes further away it decreases, this is because of gravitational forces of attraction. |
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What did Galileo do? |
Observed 4 moons around Jupiter which confirmed Copernicus' theorem that planets orbit the sun. |
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What did Newton suggest in the 17th century? |
All bodies are attracted to each other. (he he he) |
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Why do we think that gravitational collapse (that formed the universe) is prevented now? |
The universe is constantly expanding after the big bang |
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What evidence do we have that the universe is expanding? |
RED SHIFT. As the light source moves away from the observer, the wavelengths extend and move to the red end of the spectrum. |
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How is a star formed? |
Nebula clouds are pulled together by gravity. Gas gets hot and glowy (can't be seen because of the cloud.) Over millions of years it gets hot enough for nuclear fusion to take place- hydrogen is turned to helium and energy is released until hydrogen runs out. |
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What lasts longer: small stars or big stars? |
Small stars. Though they have less hydrogen, they use it slower. |
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What happens to a medium sized star at the end of its life? |
Red Giant: -Core contracts, outer cools - Turns red when it used to be yellow -Gas shells called planetary nebula are thrown -Core becomes a white dwarf and shines BRIGHT -Cools to become a black dwarf |
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What happens at the end of a large star's life? |
Red Super-giant: -Core contract, outer expands and SUDDENLY -Core collapses to form neutron star -Explosion called supernova (remnants from which can form a new star) |
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How is a black hole formed? |
Death of a large star. Core of neutron star continues to collapse and gets REALLY dense. |
