Net Work of an Closed Carnot Cycle

Step 1-2:
Step 2-3:
Step 3-4:
Step 4-1:

The Carnot Cycle

Reversible, Isothermal Expansion
Reversible, Adiabatic Expansion
Reversible, Isothermal Compression
Reversible, Adiabatic Compression
The cold thermal reservoir, at temperature TC, absorbs heat from the system in step 3-4.
Hot thermal reservoir, at temperature T H, provides heat in step 1-2.
The net amount of work done by the Carnot Power Cycle operating in a closed system is the area enclosed by the path 1-2-3-4-1:
The cylinder is insulated in step 4-1, making this step adiabatic.  When the weights are added to the piston, the pressure rises, but the volume does not decrease sharply because the temperature of the working fluid increases.
State 3 is represented in this piston-and-cylinder diagram.
In state 3b, the insulation has been removed from the ouside of the cylinder in preparation for step 3-4 in which heat trasfer into the system occurs.
In state 2b, insulation is added to the outside of the cylinder so step 2-3 will be adiabatic.
Piston-and-cylinder diagram showing state 2.
Piston-and-cylinder diagram showing the initial state, state 1.
When the weight is added to the back of the piston and heat is removed from the system, the volume decreases dramatically, but the pressure only increases modestly.
Step 1-2 is an isothermal, reversible expansion that occurs when a weight is removed from the back of the piston and heat flows into the working fluid from the hot reservoir.
This PV diagram shows the location of state 1 at high pressure and low specific volume.
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Ch 9, Lesson A, Page 3 - Net Work of an Closed Carnot Cycle