Question

The PV diagram for a 3-stage heat engine is shown below. The engine starts at point A, then to B, then C, then back to A to complete a cylcle. The units are on the axis, so keep an eye for those.

Answer 1

Shown above is the p-V diagram of a 3-stage heat engine. The engine starts at point A, then to B, and C, and then back to A completing a cycle. In the diagram, the pressure is measured in unit of kPa and the volume in mL unit.

(a) How much work does the engine do in one cycle? Pay attention to the units as usual.
J


(b) If the engine goes through the cycle 156 times in one second, what is the output power of the engine?
W

(c) Choose all that are correct from the following.

All the processes, A to B, B to C, and C to A are isobaric.
The process A to B is isobaric.
All the processes, A to B, B to C, C to A are adiabatic.
The process B to C is adiabatic.
The process from point C to A is isobaric.

a)

work done is area enclosed inside the triangle

= 1/2 * 10 x 10^-3 * 200 x 10^3 = 500J

b)

power = work / time
= 500*156 / 1

= 78000watts or 78 kW

c)

correct option:

The process from point C to A is isobaric.