Just a simple understanding question. If I obtained a DC bench power supply that has a current limit, could I test the ampacity of a wire by connecting said wire across the terminals? So when I slowly increase the current limit, more current will flow through it, causing it to heat up? A basic question but I'm learning and want to make sure this would be safe to do! Thank you :)
It is safe to do, yes. The current limiting of your power supply will only output the maximum selected current. You can do this for testing, learning by doing is always a good thing.
The question is, what you hope to achieve by this action. You will certainly see, that at some point your cable/wire is going to get warm due to the current flow, when you increase the allowed current. But you won't be able to make precise measurements and there are already tables online, that give you the values you are looking for under basically all conditions you can think of.
Therefore it will be a nice and safe to do experiment, but it does not make sense to really try to measure new data =)
and you have to control the ambient temp starting temp etc.
ampacity tables are all over the internet. look it up. don't know the wire size? measure an individual strand / count the strands - look it up in the wire tables
Ampacity values are determined be usage, insulation, inside conduit? etc. the only thing you WILL find is the fusing current. 12 ga. Cu fuses at ~12,000 Amps.
A smart person learns from others work (mistakes).... no need to do whats been done