Challenge: Problem 1

The working cycle of a heat engine using a mass of gas is represented on the mechanical plane in fig. 3.9 and on the thermal plane in fig. 3.10. Along the line a heat is taken into the working system, and along a' a lesser quantity of heat is ejected. The enclosed area in fig. 3.9 represents the work done, and this is equal to the enclosed area in fig. 3.10 which represents the heat used. Looking at fig. 3.10, what concepts could you use from amongst those on the RESPONSE ARRAY in order to describe what is involved in the cycle? Approach the problem in this way: one can first describe the process as a whole, and then one can point out what is meant by the lines a, a', b, and b' .

1
heat transfer takes energy from hotter to cooler systems 2
thermal capacity 3
isothermal change 4
a change in volume 5
transfer of energy by work, involves no change in entropy

6
latent heat 7
adiabatic change 8
a change in temperature 9
internal energy does not consist only of thermal energy 10
the internal energy periodically returns to its initial magnitude

11
conversion of work into heat production, as in the case of friction 12
a change in internal energy 13
absolute temperature-measure of the intensity of thermal energy 14
internal transition from potential to thermal energy 15
work output by system

16
a change in entropy 17
the lower the intensity at which a transfer of energy takes place, the greater the increase of its extension within the system 18
external stores of thermal energy 19
changing entropy of a system by heat transfer to a cooler system 20
the entropy associated with thermal energy at zero intensity