Carnot Cycle

Applet by Fu-Kwun Hwang

This java applet shows you the physics processes of a Carnot heat engine.

The Carnot Cycle is a four stage reversible sequence consisting of:

1. Adiabatic compression
2. Isothermal expansion at a high temperature, T2
3. Adiabatic expansion
4. Isothermal compression at a low temperature, T1
5. Back to stage 1 and continue


1. Set the starting point (Pressure, Volume) of the adiabatic compression process:
The program will show the piston position and related information as you move the mouse inside the P-V region. Click the mouse to set the initial P-V value. Before you set up the initial P-V value, you can click the horizon line and drag it to change the maximum pressure (Pmax). Move the mouse to P=1 atm, and V=22.4(liter), and check out the value of PV/nR. Do you know how many moles of gas are inside the chamber?

2. Set the starting point for the isothermal compression process:
Click the mouse button again (within the possible region).

3. Press the Start button to begin the animation; press Reset to reset the conditions.
Click + to increase speed of animation and click - to slow it down. Each click changes the time scale by a factor of 1.25.
Click the right mouse button to stop the animation; click it again to resume.
The efficiency of the heat engine will be displayed.
Different colors for the gas volume represent its temperature.

Color of the piston:
Red: contact with heat reservoir at a high T2 oC
The yellow bar within the gas volume is proportional to heat flow (in).
Green: contact with heat reservoir at a low T1 oC
The Yellow bar within the piston region is proportional to heat flow (out).
(The total length of the yellow bar is the maximum heat flow during the isothermal expansion process; some of the heat is released during the isothermal compression process.)
Blue: adiabatic process oC

4. Cp/Cv is the ratio of the specific heat of the gas at constant pressure to that at constant volume.
You can enter any value larger than 1. (Be reasonable about it!)
It will reset the program automatically.

5. While the animation is suspended, move your mouse within the PV-diagram to view the (P, V) values.