1) They are robust and don't need much maintenance 2) They don't use fuels and don't need long power cables 3)They don't cause pollution and don't contribute to global warming 4) They use a renewable energy resource
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What are the disadvantages of photocell?
1) They don't produce electricity when it is dark or too cloudy.
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What is a photocell made of?
> contains 2 pieces of silicon joined together to make a P-n junction,
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In a photocell what's the difference between the the p type silicon and the n type silicon?
The n type silicon has impurity added to produce an excess of free electrons and the p type silicon has a different impurity added to produce an absence of free electrons.
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How do photocells produce electric currents?
Sunlight contains energy packet called photons, the photons cause free electrons to move from the n type silicon to the p type silicon , this produces electric currents.
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Name the three things that the output from a photocell depends on?
1) Light intensity 2) The distance from the light source 3)The surface area exposed.
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What type of radiation does the sun produce ?
The sun produces infrared radiation with very short wavelength.
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Explain Passive solar heating...
Sun makes infrared radiation|Glass transparent to short wavelength radiation|Walls+floor of building absorbs radiation,warmsup+reradiates infrared radiation|sun hotter than walls+floor so wavelength radiated is longer-Glass reflects this back inside.
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How and why are solar reflectors moved?
Solar reflectors are moved by computers so they are always facing the sun.
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What is a wind?
A renewable form of energy
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When may a wind turbine not work?
Wind turbines won't work if there is no wind or if the speed of the wind is too great.
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What are the advantages of wind turbines?
>They do not contribute to global warming > They do not pollute the atmosphere
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What are the disadvantage of wind turbines?
> noisy > Takes up a lot of space >Some people complain that it ruins the view > It depends on speed of wind.
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Other cards in this set
Card 2
Front
What are the disadvantages of photocell?
Back
1) They don't produce electricity when it is dark or too cloudy.
Card 3
Front
What is a photocell made of?
Back
Card 4
Front
In a photocell what's the difference between the the p type silicon and the n type silicon?
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