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This text is meant to accompany class discussions. It is not everything there is to know about the basics of torque and the two conditions of equilibrium. It is meant as a prep for class. More detailed notes and examples are given in the class notes, presentations, and demonstrations (click here.)
Questions Click for the questions that go with this reading
Heat Engines

The work and eficiency of a heat engine can be determined by the thermal energies into and out of the system during a thermodynamic cycle.

This video can be found on YouTube at


Carnot Cycle


Sadi Carnot, in 1824, proposed that the maximum efficeincy would occur is all the thermal energy, measured in Kelvins, was transfered directly to and from the energy reservoirs into and out of the heat engine during a cycle. (This means no loss in thermal energy as can occur in the setup above.)

This video can be found on YouTube at


Power: Review and Application

Power is defined as how quickly energy is delivered or received.


power Equation


The area on a PV diagram that shows a cycle is the work of the gas. In a heat engine this cycle occurs over and over at regular time intervals. The time in the power equation's denominator is the time to complete one heat engine cycle. This is refered to as the period.

The frequency is the measured in Hertz, [Hz.] It is the inverse of the period. Therefore,



Where "f" is the frequency in Hz.


This Caterpillar mining dump truck is one of the largest dumptrucks in the world. (Look at the ladder at the front of the truck to get into the driver's seat.) Everytime a cylinder in its engine moves up and down, it completes a themodynamic cycle that can be picutred on a PV-diagram. IF the thermodynamic cycle of the cylinder is shown below, then how much power is generated by each stroke when the engine is running at 2000 rpm's, 33 Hz.


Reading Quiz
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by Tony Wayne ...(If you are a teacher, please feel free to use these resources in your teaching.)