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

New Trends in Physics Teaching IV
APPENDIX 2
A selection of other statistics
1. The daily energy requirement of a human being depends on his or her mass and the work
being done. Some average figures (all in kJ per day) for adults are:-
Men
Women
Lying in bed
Light work
Heavy work
7400
11 600
14 700
6300
9500
12 500
As a rough average one can take 10 000 kJ per day, which is a little more than the energy
transformed by a 100 W lamp in 24 hours (8640 kJ).
2. Power station efficiencies (about 30 per cent)
Fuel - 1000 units
850 units
Flue Gases
150 units
Steam Turbine
and Alternator
I
Cooling Water
550 units
Electrical Energy
300 units
Note that these efficiencies determine the efficiencies of energy conversions in the electrical
appliances used in industry and in the home.
3. A special problem in temperate and cold climates
Heat losses from houses: through the roof 25 per cent
through the windows 10 per cent
through the walls 35 per cent
through the floors 15 per cent
through draughts 15 per cent
4. Energy costs in manufacture
A tin of beans
A colour television set
A small motor car
11 OOOJ
25 000 MJ
80 000 MJ
18