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Illustration 21.1: Carnot Engine

engine cycle:

Please wait for the animation to completely load.

There is a time delay-since the system must be in equilibrium-before the initial change of state occurs.

You must go in order.

In this animation N = nR (i.e., kB = 1). This, then, gives the ideal gas law as PV = NT. Restart.

There are four steps to the Carnot cycle: a combination of isothermal and adiabatic expansions and contractions. Which of the steps are isothermal and which are adiabatic? Make sure to step through the animation in order. During step one the gas does a positive amount of work. Step two is adiabatic, with the gas doing a positive amount of work. During step three there is a negative amount of work done by the gas. Finally in step four, which is adiabatic, the work done by the gas is negative. Notice that the total work done (the remaining area) is positive because positive work is done at high temperatures and negative work is done at lower temperatures. During step one heat is absorbed (Q > 0) and during step three heat is released (Q < 0). More heat is absorbed than is released for the entire cycle. This is the basis of how engines work: Heat (from the hot reservoir) is transferred into mechanical work (piston moving).

Illustration authored by Anne J. Cox.

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