4F30.70 • Heat Engine Cycles

Photo of University of Texas at Austin's Demonstration:

Faculty Instructions:

• Data collection with the lab computer is optional for this demonstration.
• Begin by immersing the can in the cold bath.
• Once it has reached equilibrium, the piston should still be about 2-3 cm from the bottom of the cylinder.
• Now, place the mass on the piston and immediately immerse the can in the hot bath.
• Observe the piston pushing the mass upward as the air expands.
• Once it has reached equilibrium, remove the mass from the piston and move the can back into the cold bath.
• Observe how the piston returns to its original position.

Concepts Conveyed:

• This demo consists of a heat engine of air inside a cylinder which expands when immersed in hot water.
• The expanding air pushes on a piston and does work by lifting a provided weight.
• The cycle is completed by immersing the can in cold water, which returns the air pressure and volume to their initial states.

Demo Staff Instructions:

• Ensure the mass hanger is attached with 35 g of mass. This acts as a counterweight for the piston.
• Displace the piston 2-3 cm from the bottom of the cylinder.
• Prepare a hot (~80 degrees C) and cold (lots of ice!!) bath.

Last updated on March 9, 2023