cross-posted from: https://programming.dev/post/48079645 because it was headshotted within five minutes without any explanation. :/
In the laundry room where I live, there is this machine.
The fan in the back blows air onto the heating elements that heat up the air, which in turn hits the laundry, speeding up the evaporation of the water.
I have no formal education on electricity, I’m just extremely interested and eager to learn. I think I understand that the rods heat up because enough current is “pushed” with enough voltage through this material that has enough resistance for it to heat up.
If these are the hot and neutral rods next to each other (which I visually believe I confirmed) with no insulator in between, why is there no arcing?
What are prerequisites for arcing? I guess, if arcing occurred so easily, then we would have a lot more ground faults and short circuits all over electrical installations?
I don’t have much experience with heating elements specifically, but hers what I found;
This type of heating element is called Calrod (a trademarked name). Here’s a cross section :
As you can see, there’s stuff inside the visible tube. The spiral inside is the actual “wire”, through which current flows, and that heats up (see also: Joule’s Law).
Then there’s a layer of magnesium oxyde, which is an insulator. This is what keeps the current from going away from the wires.
The outside sheath that you see is just some stainless steel tubing that keeps the (powdery) magnesium oxyde in.
On the topic of arcing; an arc is a very specific phenomenon. Usually, air is an insulator. However, under very high voltage, current can start to cross air gaps. In doing so, it heats up the air a lot, creating a plasma. This plasma conducts electricity (at least it can do so better than plain air), so once the air is “broken”, current can flow through the air gap. I don’t know the exact numbers, and it depends on the gap size, but an arc requires at least a few kilovolts to appear.
Sidenote: when you get a zap when touching something metallic after you’ve worn slippers, that’s because you’ve actually gained a few kilovolts of charge compared to the metallic thing, and you’ve made a (very short lived) arc!
Thanks for the reference to Joule’s law and to static discharge! :D And great image of a Calrod element!