A “proper” course in Thermal physics should ideally include labs based on (a) measurement of quantities ( eg: pressure, temperature, heat), (b) verification of physical laws (gas laws, isothermal and adiabatic processes) and (c)observation of new and interesting phenomena (Boltzmann distribution, Phase transitions). In the online version, we put together a kit with equipment that is easily available, cheap and portable, but also retains the essential features listed above.
The kit included:
- Scalp vein tube
- Measuring flask
- Sodium Thiosulphate
- 5 ml syringe
Home kit-based experiments
The course had a variety of activities that included some computational ones as well. Some experiments were a little less demanding (checking the anomalous expansion of ice) than others ( measuring specific heat using ice calorimetry). I have highlighted the following two components of the kits and included the experiments done with them. These are two “big things in small packages” that turned out to be very useful.
The thermistor is a small piece of semiconductor, whose resistance decreases with temperature. If we assume quantities such as the band gap of the semiconductor, we can use a thermistor to estimate the value of the Boltzmann constant. This is a terribly easy experiment to do, and it couples well with a discussion of the Boltzmann distribution.
The thermistor turned out to be useful in other ways: (a) some students received broken thermometers, so they calibrated the thermistor against a few known proportions of ice cold and boiling water, and used it as a thermometer (b) one can carefully stick the head of the thermistor inside a syringe, with the leads sticking out, and seal the syringe, by melting the plastic and pressing it down with tongs. I used this to demonstrate how temperature changes in an adiabatic process. The temperature change is very small, but detectable using this device. Cost: Rs 10.
The title for the handout is “Boltzmann distribution”. It includes a couple of activities with the thermistor and one computational activity using a spreadsheet.
Example student report
A sample report with names scrubbed and/or with student’s permission. The report may be a pdf and the image below might be a sample submission image/video (ideally < 10 MB)
Scalp vein tube
This is a thin flexible plastic tube of inner diameters of 1-3 mm. The tube is open on one end and has a cap that open and close the other end. This was used in an experiment to verify Boyle’s law, measure atmospheric pressure, and to just understand pressure in a fluid. This can also be used to verify Charles’s law, but that would have required a drop of mercury or sulphuric acid. For Boyle’s law, we can just use water. This is a versatile object, and can be used creatively to design a number of experiments, by coupling to syringes, pressure gauges, etc. Cost: Rs 25.
This handout includes instructions for an experiment that uses the scalp vein tube to verify Boyle’s law and measure atmospheric pressure. A drop of mercury is used in the experiment when done in the lab, but a column of water serves the purpose just as well.
Reception and feedback
The kit was quite minimal, put together and sent quickly. Rema and I sat down and made a list of essentials, and we had to buy, pack and send, within a few days. At the time, we could not assume that everyone would even receive the kit in one piece. One student didn’t receive the kit at all (later I learned that this would not have happened if I had used speed post). The experiments went well, but with just a few more syringes, maybe some play-dough and a weighing scale, some more experiments could have been done. Still, the students appreciated the fact that there were some experiments, and didn’t seem too burdened by them either.