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Challenge: Problem 3

The situation discussed in Problem 2 is part of a cycle of changes that occur in the cylinder. Now, any change in a system can be reduced to a combination of a change by heat and a change by work. For simplicity, we restrict heat transfer to the con-Jition that the temperature does not change. In the Jiagram, there is represented the behaviour, in terms of pressure and volume, of some mass of gas involved in such a cycle of changes.

The line b represents an isothermal (temperature constant) compression. The line a represents an adiabatic (no heat transfer) expansion. The cornbination of a and b (rather as with vectors) produces movement from state (P, V) to state (P, V). Temperature T > Temperature T. Visualize how any two states (represented by two points in the graph) can he connected by the right combination Df adiabatic and isothermal steps. Set down the conditions represented by the lines c and d, so that you are able to compare them with each other.

1
U = 0		 2
conversion of work into internal energy by compression		 3
transition of energy from potential state to thermal state		 4
conversion of internal energy into work by expansion		 5
Q = 0
6
transfer of energy through adiabatic enclosure		 7
specific heat		 8
heat transfer		 9
W = 0		 10
enclosure permitting transfer of energy by heat and by work
11
change of phase of the kind: liquid vapour		 12
chemical energy		 13
U 0		 14
T 0		 15
H 0
16
thermal equilibrium		 17
uncertainty of change in U		 18
V = 0		 19
P = 0 		20
T = 0