this post was submitted on 23 Nov 2023
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I just tested this (for science!) with a 9V battery and an iron nail of roughly nose-ring diameter. Both the nail and the battery get unpleasantly hot after several seconds. I don't think they'd get hot enough to burn you, though. (Don't take my word, though, please!) I believe the internal resistance of the battery does also increase with the temperature, so it effectively somewhat self regulates itself.
Common nose ring materials like Titanium and Stainless Steel are 4× and 7× more resistant than iron, which means they should dissipate more power than the nail, and thus get hotter. I was calculating something around 3 milliohms for a titanium 16 gauge 10mm wire, and 0.7 milliohms for an iron wire.
Regardless of material, at 1000 milliohms internal resistance, i think the battery itself is doing most of the heat dissipation. (But also over a much bigger surface area!)
/c/theydidthescience
How long did you keep the nail on the battery for?
A 9V battery can be used as a foam cutter.
Styrofoam and most art foams melt at about 200°C
https://youtu.be/4Hj9PJstexk?si=_NEMZZU4Yu_CSN0a
About 10-20s, I left it on until it didn't seem to be getting much hotter. I also didn't want the battery to overheat and fail catastrophically. I think because the "wire" is such a high gauge, there's not enough current for it to get seriously hot. In a foam cutter, you're passing all that current through a much smaller cross-sectional area.
Here is an alternative Piped link(s):
https://piped.video/4Hj9PJstexk?si=_NEMZZU4Yu_CSN0a
Piped is a privacy-respecting open-source alternative frontend to YouTube.
I'm open-source; check me out at GitHub.
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