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

New Trends in Physics Teaching IV
Teaching Hints:
1. The solar cooker is best used between about one hour before and one hour after the sun
crosses the meridian during the summer and/or dry season months.
2. Aluminium foil is pasted in all sides of Box B to prevent heat losses, reflect radiation to the
cooking area, and to prevent radiation outside the box.
3. The solar cooker can be placed outside as soon as the sun shines to store heat inside.
4. Twelve eggs can be cooked in the can with 400 ml water in one and a half hours, between
1100 and 1300 hours. The eggs should be in a single layer.
Sample Data for Solar Cooker
I. Boiling Water
Time
Temperature of 300 ml
of water outside the cooker
("C)
Temperature of 300 ml
of water inside the cooker
("C)
Weather
Condition
09.30
09.45
10 .oo
10.15
10.30
10.45
37
37
39
40
41
41
37
58
84
94
100
100
sunny
sunny
sunny
sunny
sunny
sunny
I1 Boiling Eggs
Time
09.30
09.45
10.00
10.15
10.30
10.45
1 1 .oo
11.15
11.30
11.45
12.00
eggs were cooked at 11.15 a.m.
Temperature of eggs and 300 ml
of water inside the cooker
("C)
30
34
35
37
45
50
65
75
82
90
100
Temperature of 300 ml
of water outside the cooker
("C)
30
32
32
32
35
37
39
41
41
42
42.5
Weather
Condition
sunny
sunny
sunny
sunny
sunny
sunny
sunny
sunny
sunny
sunny
sunny
308