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My electric stovetop developed a fault which caused a short circuit inside the unit (sparks flying and all). The fault occurred as one of the knobs came loose and the metal strut that was supporting it fell down into the unit. The casing of the stovetop is earthed to a nearby power socket, with a resistance of 0.5 ohms. There is no RCD installed on the circuit. No circuit breaker or fuse was tripped during the fault, and immediately after it occurred I turned the circuit off at the fusebox.

Here's the part that confuses me. A clean metal teaspoon was lying on the casing of the stove but not anywhere near the heating element. It wasn't touching anything else. Immediately after I turned the stove off, I realised that the spoon actually got stuck to the casing of the stove - I had to apply quite a bit of force to pull it off, and there was a very small but noticeable ridge that could be felt with my fingers on both the spoon and the stove where they were touching.

My question is, how could the spoon have bonded to the stove if there was no way for it to have a potential difference (i.e. it wasn't touching anything else except the metal casing of the stove?). Is there some physical explanation that doesn't require current to flow through the spoon (and thereby explain heating as a result of resistance?). The spoon was made of stainless steel.

Obviously, I've had an electrician look at it, but apart from checking that it passes the earth test, he couldn't give me a reason why the spoon could have bonded to the stove, nor why the circuit breakers weren't tripped.

I am not an engineer by the way, although have some basic technical and physics knowledge (coming over from stats and data science SE).

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  • \$\begingroup\$ I've welded things in the past without tripping a relay. No question you welded the spoon to the casing: sparks flew, spoon was hard to remove, ridges, etc. All the signs. What's mysterious is exactly how that happened. But that's just ignorance. And we humans have an unlimited supply of that. You said a metal strut "fell down into the unit." But it could also be that you've got neutral and hot wired incorrectly on a nearby plug nearby and you just aren't aware yet. I've seen that, too. Lots of possibilities. Perhaps someone in EE.SE has a working crystal ball. \$\endgroup\$ – jonk Oct 6 '16 at 6:02
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Although there is a earth connecting to the casing of the stove that does not warrant that all parts of the casing are indeed well connected to earth. Frequently the extra earth wires are not or no longer well connected to the mainframe and therefore not earth properly. This leaves room for the current to flow along many ways and most probably the spoon has been in such a path making it welded against the casing. Since we can not see the actual situation more can not be said.

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