Thermodynamics (Physics)

A thermodynamic system is taken from an original state A to an intermediate state B by a linear process as shown in the figure. Its volume is then reduced to the original value from B to C by an isobaric process. The total work done by the gas from A to B and B to C would be : [figure]

1. 800 J
2. 2200 J
3. 33800 J
4. 1200 J

Answer

(1) 800 J

Solution

[figure]

WAB+WBC = area of triangle ABC

WAB (expansion) = area under AB (+); WBC (compression) = - area under BC.

W= 12 (7-3) m3 (8000-4000) dyne/cm2

=8000 dyne cm-2 m3

1 dyne/cm2= 10-5 N10-4 m2=0.1 Pa

W=8000 0.1=800 J

Answer: (1)