My son is doing a science experiment on how varying temperature and diameter of wire impacts the resistance. We are assuming we can accomplish this by using different gauge wires, a home thermometer, and a basic digital multimeter (e.g. this one at amazon).
Is this correct, or is the multimeter only used to measure resistance of batteries and circuits and not a plain piece of wire? If this setup is not sufficient, can you suggest an alternative?
Regarding temperature, will a simple home thermometer (battery, not mercury) be sufficient?
Best Answer
Hmm your experiment sounds like a good idea but I think it'll be much harder than you're imagining. The resistance of wires is very low. After all, they are designed to conduct! Check out this table. 30 gage wire has a resistance of $0.1\: \Omega/\mathrm{ft}$ which is well below what a typical multimeter can read.
Also, because the resistance is so low, one very big source of error will be how well the multimeter probes are attached to the wire. You'll likely end up measuring the resistance at the point of contact as much as the resistance of the wire.
One way to help though is to measure very long wires. If you can get wire a few hundred feet long the resistance of the wire will start to be high enough that meaningful measurements can be made, despite experimental error.