2018 BFY III Abstract Detail Page
Previous Page |
New Search |
||W28: Thermal Diffusion in Cylindrical Rods: Measuring Specific Heat and Thermal Conductivity
||We present an experiment to measure thermal diffusion in cylindrical rods. From one measurement, using analytical solutions to simple heat flow equations, we can find both the thermal conductivity and the heat capacity of the material to within 5% of the accepted values.
This experiment gives students the opportunity to explore energy transport that occurs not as waves but rather via diffusion. A heater applies a point source of energy to a rod, and this energy then diffuses through the rod, changing the temperature of the rod along its length. The temperature change along the rod is measured via multiple thermistors, and this temperature difference can be fitted to the thermal diffusion equation solution (with specific heat and thermal conductivity are fitting parameters). A simple circuit controls the energy flowing into the rod via a heater and amplifies the voltages from multiple thermistors. This circuit can be controlled manually or via a computerized interface (e.g., LabView, Matlab, or Arduino interfaces). In this experiment, students gain experience both with a simple difference amplifier and a FET switch, the thermal diffusion equation, and non-linear fitting.
In addition, this experiment can be taken as is or expanded. Students can expand upon the data analysis, adding elements such as convective heat losses or numerical models that include the finite size and finite duration of the heater. Students can also expand upon the experiment by adding different materials to test or using additional thermistors to measure the temperature. Finally, students can improve the experiment and make the data match the model better by removing convective heat losses and relocating the experiment to a vacuum. Full details are discussed in Sullivan et al., Am. Jour. Phys. 76, 637 (2008).
Matthew C. Sullivan
Department of Physics and Astronomy
953 Danby Rd
Ithaca, NY 14850
|Workshop Doc 1:
Download the Workshop Doc 1