New trends in physics teaching, v.4; The ... - unesdoc - Unesco

New Trends in Physics Teaching IV
Solar cushions
Made from
A range of impermeable materials:
black polythene, silver reflective
mylar, transparent polythene,
golden mylar, etc.
Waterproof sticky tape
Plastic tube, rubber bungs
Thermometers
Construction
25 cm squares of materials are stuck together with waterproof tape in different combinations of
upper and lower surface; black/black, transparent/silver, clear/black, etc. (figure 2). A short
length of plastic tubing is fitted to enable the ‘cushions’ to be filled.,
Experiments
A litre of water is poured into each ‘cushion’. Its temperature is taken and the cushions are laid
flat in the sunlight for half an hour. Temperatures reached are compared to find the best combination.
This experiment can be varied by using larger or smaller masses of water, by changing the
time, by insulating the underside and by putting the filled cushions in large plastic bags, blowing
them up and sealing them. Or put the ‘cushions’ under gardeners’ cloches.
Figure 2. Solar cushions.
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