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Physics Unit 2
Living For The Future...…read more

Slide 2

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Using the Sun's energy
Some of the energy given out by the sun is stored here on earth
as fossil fuels.
But we can also use the sun's energy in a more direct way:
Solar cells
Solar cells generate Direct Current (the same as a battery)
Solar cells are made of silicon-a semiconductor. When sunlight
falls on the cell 2 this happen...
1)the silicon atoms absorb some of the energy, knocking loose
some electrons
2)these electrons then flow round a circuit as electricity!
The power output of a solar cell depends on:
Its surface area (the bigger the cell, the more electricity it
produces) and the intensity of the sunlight hitting it (brighter
light=more power).
Sun's energy knocks flows
off electrons…read more

Slide 3

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Using the Sun's energy,
Solar cells (or photocells) have LOTS of advantages:
1)There are no moving parts ­ sturdy, low maintenance and long lifetime
2)You don't need power cables or fuel
3)Solar power will not run out and it does not pollute the environment!
But there is one major disadvantage:
1)No sunlight = No power!
Passive solar heating:
1) solar panels ­ these are much less sophisticated than photocells; all they are is
black water pipes inside a glass box. The glass lets heat and light in from the sun,
but does not let it out so easily. This heat is then absorbed by the black water
pipes and hot water is sent around the home.
2)carefully designed buildings- can use energy more efficiently e.g. Which way the
windows face.
3)Cooking with solar power ­
using a curved mirror, then you can focus the Sun's light and heat.
i.e. all the radiation directed at your curved mirror
is focused right onto your food.
food…read more

Slide 4

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Lets see how well you know it
Name one advantage and one
disadvantage of using solar cells? [2]
Explain how solar cells work. [3]
Explain the difference between solar cells
and solar panels. [3]
1) disadvantage: no sun = no power, advantages: no moving parts, no power
cables or fuel, solar power is renewable/good for environment.
2) silicon atoms absorb energy, knock off electrons, electrons flow to create
current (DC)
3) solar panels are just black water pipes in glass box, heat and light is absorbed
by the black pipes rather than silicon atoms, water is heated rather than electricity
made.…read more


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