Elenco Solar Energy - Manual (Page 11)

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Experiment no.12 Singeing a piece of rubber
As you approach the focal point of the parabolic reflector with a piece of rubber, the
latter begins to smoke and smell. The rubber will help you to determine the
approximate area around the F.P. at which the sunlight is concentrated.
Experiment no.13 Cold water in sunlight
Half fill a test tube with cold water and attach it to the test tube holder.
Measure the temperature of the water and then place the holder and test tube into
direct sunlight for 5 minutes. How great was the rise in temperature?
Experiment no 14. Dark liquids in sunlight
Repeat the last experiment but this time, add a few drops of ink (See Exp.5.)
How great is the rise in temperature now?
Experiment no. 15 Influence of ink
Repeat the last experiment with water coloured with a few drops of ink.
The water should boil. How long does it take to bring the water to boil?
Can it be done in winter?
Experiment no. 16 Brewing tea
Place a few tea leaves (less than ? teaspoonful) into a test tube and add enough water
to half fill it. Fit this into the solar furnace. See how long it takes to brew yourself a
“cup of tea.”
Never drink directly from a test tube.
Experiment no. 17 Melt a candle
Insert a small candle into the test tube and bring it into the F.P. of
the reflector. The candle will melt.
NOTE: In this experiment you will dirty the test tube with molten
wax and it will be difficult to clean. To do so you need soap, hot
water and a test tube cleaner. You can make one by wrapping a little
steel wool around a pencil or suitable stick. Clean it carefully.
Experiment no. 18 Frying an egg white
Take an uncooked egg and separate the white from the yolk. Pour some of the egg
white into the test tube. Bring this into the F.P. of the solar heater.
Can you cook the egg white? How long does it take to make it hard?
Solar energy is used for cooking in remote areas of the world.