One
mole of an ideal monatomic gas is caused to go through the cycle as
shown in the figure. (a) We
have to find the work done on the gas in expanding the gas from
a to
c along the path abc.
(b) We have to find the change in internal
energy and entropy in going from b
to c.
(c) We have to find the change in internal
energy and entropy in going through one complete cycle. We have to
express all answers in terms of the pressure
|
Solution: Click For PDF Version (a)
The working
substance undergoing the cyclic process shown in the figure is one
mole of a monatomic ideal gas. At the state a
the temperature of the gas can be found from the ideal gas equation
of state as we know pressure and volume of the gas there are
The work done on the gas during its isobaric expansion from a to b will be
And, as the change from c to b takes place at constant volume, no work is done on the gas during this part of the cycle. Therefore, the work done on the gas during the expansion from a to c along the path abc will be
(b) Change in the internal energy of the gas from b to c will be
We calculate the change in entropy between c and b. As the process b to c takes place at constant volume, heat absorbed
And,
As
we find
(c) As the process is cyclic, the change in internal energy and entropy in going through one complete cycle will be zero. |
and volume
at
point a in the diagram.
