PASCO TD-8565 Adiabatic Gas Law Apparatus - Manual (Page 24)

© 2009 Physics Enterprises 24
A careful examination of the adiabatic data (Experiment 3A) shows a slight time delay
between the piston reaching the minimum volume and the pressure achieving its
maximum. The amount of delay is on the order of the height of the cylinder divided by the
speed of sound. You can adjust the pressure to account for this delay. Drag-and-drop the
Graph icon onto P and the Graph1 icon onto V so that both Pressure and Volume are
displayed on the same scale. Moving the cursor to the numbers on the horizontal scale and
sliding allows you to expand the view until the small time delay between the abrupt
minimum in the Volume and the slightly delayed maximum in Pressure becomes notable.
Use the XY cross hair tool to record the two times to within a millisecond:
t
min Vol
= ___________ s t
max P
= ___________ s
Calculate the pressure time delay,
∆t = t
max P
- t
min Vol
= _________ s (should be a few milliseconds)
Use the Calculator to compute the corrected pressure assuming the first order in a Taylor
series expansion of the pressure with time,
(3.6a)
Note that derivates are available under the Special functions found in the Calculator.
Use the Calculator to compute the ln(P
corr
) and ln(V) and make a graph of ln(P
corr
) on the y-
axis vs. ln(V) on the x-axis. Perform a linear fit and record the slope:
Slope = γ = __________
Has the introduction of pressure time delay into the analysis improved your results?
t
dt
dP
P P
corr
Δ ⋅ + =
Appendix B: Additional Analysis to Improve
Adiabatic Gas Law Results