We describe a new version of the Rüchardt experiment in which we record the time evolution of temperature, pressure, and volume oscillating around an equilibrium value. We use a portable microcomputer-based laboratory made of a graphic calculator, an interface, two commercial sensors (sonar and barometric sensor), and a homemade temperature sensor.

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Grimellini Tomasini
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See, for example, M. W. Zemansky, Heat and Thermodynamics (McGraw–Hill, New York, 1957), Chap. 5, where the method of Katz–Woods–Leverton to account for the departures from ideal adiabatic process is also mentioned.
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A reversible thermodynamic transformation is an ideal process that goes through equilibrium states, and therefore the time derivatives of volume and pressure must be small. This may be approximated with phenomena involving large changes of P and V by proceeding slowly or with fast phenomena by involving small P and V changes.
7.
This assumption is justified for oscillations with relative pressure and volume changes of a few percent, for frequencies up to a few Hz.
8.
We used a TI-89 hand-held graphic calculator and the CBL interface produced by Texas Instruments, with barometric probe BAR-DIN and Motion Detector, MD-CBL, produced by Vernier Software, Portland, OR.
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Values measured for the period τ should be corrected for the damping effect, e.g., assuming a viscous drag, τ≈τmis{1−(λ/π)2}, where λ is the logarithmic decrement of the oscillation amplitude, or τ≈τmis{1−(τ/2πτ0)2}, where τ0 is the oscillation decay time. In our case this effect is negligible [with τ≈1 s and τ0≈3 s, we get (τ/2πτ0)2≈0.3%].
11.
This apparatus was patented and is now produced by MAD, Italy (grolive@tin.it).
12.
We used a model produced by Chicco®, Italy.
13.
The period was measured by selecting, on the graphic calculator screen displaying the distance versus time plot, the coordinates of maximum or minimum elongation. The half-period was then derived as the mean value of the selected time intervals.
14.
Purely adiabatic transformations are not physically achievable because thermal coupling of the gas with the vessel walls is always present. Even if they were achievable, it would not be possible to measure the temperature in a transformation which is strictly adiabatic: Some energy in fact must be transferred to or drained from the system to obtain a measurement of its temperature. Therefore the definition “adiabatic” for a real process should always be taken as meaning “approximately adiabatic.”
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