Question

The net work done through a series of changes reported in figure at the end of cycle for an ideal gas is equal to:

• A. Zero
• B. –2pv
• C. –3pv
• D. –5pv

Answer 1

Answer: (C)

–3pv
The work done of the system is calculated by taking the product of pressure and change in volume in the system.
In the graph, Work is done by taking the product of the height of the triangle and the length of the base of the triangle and dividing it by 2.
Work done =$\frac{1\times height\times base}{2}$
The value of height will be the change in the pressure, we can see that pressure changes from 4p to p, and the length of the base changes in volume, the volume changes from 3v to v. since work is done by the system, the value will be negative, putting the values, we get:
Work done: -$\frac{1}{2}\times (4p-p)\times (3v-v)$
Work done : -$\frac{1}{2}\times 6pv$=-3pv