Question: 31. A thermodynamic system is taken through the cycle abcda. The work done by the gas along the path bc is :
(1) zero
(2) 30 J
(3) -90 J
(4) -60 J
Answer: Option (1)
Explanation:
The work done by a gas in a thermodynamic process is given by
W = \int P \, dVFrom the P\text{-}V diagram,
the path bc is a vertical line.
A vertical line in a P\text{-}V
diagram represents a constant volume process.
Hence, along path bc,
the change in volume is zero, that is
dV = 0Substituting in the work expression,
W = \int P \cdot 0 W = 0Therefore, no work is done by the gas along the path bc.
Hence, the correct answer is Option (1).