- #1
Burningmace
- 14
- 0
Back when I was doing A-Level physics we were given a coursework assignment that seemed rather ridiculous, which I've been thinking about recently. We were charged with measuring the electrical resistance of a standard household brick at different temperatures, using only equipment we could find in a school lab. Our teacher thought it was insane, as did I. I got a second opinion from my father (he's an electronics engineer that works on diesel-electric locomotives), and he said the only way to do it realistically would be to use a Tesla coil, and that's not exactly something schools just keep in the store room. The solution they were looking for turned out to be a Wheatstone bridge, not that it'd ever work.
The obvious issues:
1) Bricks aren't solid and have higher resistance than air, so any current being passed through is more likely to arc round the brick through the air. Only solution - do the experiment in a vacuum.
2) Heating a brick to 600C uniformly in air isn't an easy task with lab equipment, let alone in a vacuum.
3) Generating the extremely high voltage required to pass a current through the brick is a big problem.
4) Measuring the resistance at such high voltages is practically impossible without special equipment.
I ended up writing that the experiment was impossible using lab equipment - the closest thing even vaguely plausible would be to use an EHT supply with a Wheatstone bridge, with a heat-resistant bell jar to heat the brick in a vacuum, then went on to describe experiments that were more likely to yield a result.
I know the electrical resistance of bricks has been measured before for lightning safety purposes, but these experiments would have used Tesla coils to generate extreme voltages.
Anyone think of something we missed?
The obvious issues:
1) Bricks aren't solid and have higher resistance than air, so any current being passed through is more likely to arc round the brick through the air. Only solution - do the experiment in a vacuum.
2) Heating a brick to 600C uniformly in air isn't an easy task with lab equipment, let alone in a vacuum.
3) Generating the extremely high voltage required to pass a current through the brick is a big problem.
4) Measuring the resistance at such high voltages is practically impossible without special equipment.
I ended up writing that the experiment was impossible using lab equipment - the closest thing even vaguely plausible would be to use an EHT supply with a Wheatstone bridge, with a heat-resistant bell jar to heat the brick in a vacuum, then went on to describe experiments that were more likely to yield a result.
I know the electrical resistance of bricks has been measured before for lightning safety purposes, but these experiments would have used Tesla coils to generate extreme voltages.
Anyone think of something we missed?