PASCO TD-8565 Adiabatic Gas Law Apparatus - Manual (Page 19)

Experiment 4: Complete Cycle
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1. Quickly compress the piston in an adiabatic compression stroke, continuing to hold the
piston down at the bottom of the stroke. (Stroke 5 to 4 in the Otto cycle diagram).
2. Hold the piston down while an isovolumetric (isochoric) transfer of heat out of the system
takes place. Continue to hold the piston down until you observe that the pressure is no
longer dropping (approximately ½ minute). (Stroke 4 to 3 in the diagram).
3. Quickly raise the piston in an adiabatic expansion and hold up at the top of the stroke
(Stroke 3 to 6 in the diagram).
4. Continue holding the piston up until the cycle on the P-V curve is completed. (Stroke
6 to 5 in the diagram).
Analysis
A. Retake the adiabatic compression stroke only while examining the plot of P vs. V. Use the
Σ statistics button to evaluate the area under this high-pressure, adiabatic curve. (For
numerical reasons, avoid the end points of the P vs. V curve!)
W
on
= area
upper
= __________ J
B. Retake the adiabatic expansion stroke and measure the area under this lower pressure
curve. (Again avoiding the end points).
W
by
= area
lower
= __________ J
C. Calculate the ratio,
=
−
=
on
by on
W
W W
ξ
__________
Procedure
Set up the experiment as in Experiment 3 (Adiabatic Gas Law), converting voltages into
Pressure, Volume and Temperature. Set up a plot of Pressure vs. Volume. Put the two pins in
the device to limit the motion of the handle. Raise the piston, open the stopcock and allow
the cylinder to come to equilibrium with its surroundings. Close the stopcock. Once you Start
the data collection, perform the following four steps before you Stop: