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Below is a copper coil, presumably forming an electromagnet. From my understanding the electrons travel around the coil to produce a magnetic field. But why don't the electrons jump the wires and take the shortest path?

Below I tried to draw the path that would make sense (for me) for the electrons to take:

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    \$\begingroup\$ The wire is coated with an insulating layer. \$\endgroup\$
    – chamod
    Aug 21, 2019 at 4:24
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    \$\begingroup\$ Are such coils always insulated? Even those really small wires forming a coil? \$\endgroup\$
    – rrswa
    Aug 21, 2019 at 4:28
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    \$\begingroup\$ @Ruan Especially that so-called "magnet wire". \$\endgroup\$
    – DKNguyen
    Aug 21, 2019 at 4:41
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    \$\begingroup\$ @Ruan I'd say they're always insulated because when we put a coil in a system we want the electricity to have to flow through it rather than taking a shortcut. I only hesitate with "always" because there may be some super-exotic situation where you wanted the short. Perhaps there's a time where you want a solid ring of copper connected to something, but due to some mechanical properties you want to make it out of wire rather than one solid chunk. I can't think of any cases of that happening, but electrical engineers are a clever bunch! \$\endgroup\$
    – Cort Ammon
    Aug 21, 2019 at 15:51
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    \$\begingroup\$ @Ruan coils can be made from bare wire, but they have to have loose turns (not touching), and can't handle high voltages. There aren't many commercial situations where this is useful, but you might see it in a hobby project. \$\endgroup\$
    – hobbs
    Aug 21, 2019 at 16:25

2 Answers 2

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This type of wire, used for making coils, is commonly called "magnet wire". https://en.wikipedia.org/wiki/Magnet_wire

It looks like it's bare copper, but it's actually coated with a very thin layer of transparent insulation. Otherwise, you're absolutely right -- if the wire were really bare, the coil wouldn't work because the current could cut straight across from one lead to the other.

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    \$\begingroup\$ That makes sense, for some reason i couldn't find an answer online, thanks \$\endgroup\$
    – rrswa
    Aug 21, 2019 at 4:31
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    \$\begingroup\$ The windings are layered carefully, particularly on high voltage devices, so that adjacent layers do not have large potential differences. This reduces the stress on the insulation layers so it doesn't matter if they are thin or suffer damage. \$\endgroup\$
    – rolinger
    Aug 21, 2019 at 13:54
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    \$\begingroup\$ And if you've ever made the mistake of thinking this is just bare wire, you find very rapidly that you can't solder to it because the insulation burns and then gets in your way, preventing adhesion. When soldering such wire, one typically has to chemically strip the end so that it isn't insulated first. \$\endgroup\$
    – Cort Ammon
    Aug 21, 2019 at 15:53
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    \$\begingroup\$ And accidental damage to the insulation (or cracking caused by heat or corrosive environments or excessive inductive motion of the coil or ....) causes shorts in which the current does short-cut along the way which makes the magnet less effective. \$\endgroup\$
    – dmckee --- ex-moderator kitten
    Aug 21, 2019 at 22:43
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    \$\begingroup\$ @CortAmmon Depending on the thickness one can strip the insulation off the end by just dipping it in molten solder (on the tip of your soldering iron) for a few seconds. You'll see it smoking which is the lacquer burning off \$\endgroup\$
    – slebetman
    Aug 22, 2019 at 0:45
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Sometimes they do take the shortest path, when they are not supposed to. As others have said, the wires are normally insulated. However, if a current flowing in the magnet is suddenly interrupted by (say) an open circuit the voltage will rise until those electrons "get out" - either by sparking across an air gap or breaking through the insulation.

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  • \$\begingroup\$ Think about the water in your pipes. The water flows in the pipes as long as the pressure is not to great. But at sufficiently high pressure, the water gets out and eventually flows to the lowest point available. This could happen if a very high voltage is suddenly applied to your inductor. Of course the inductor can fail in other ways: excessive current for too long will cause heating that destroys the insulation and you will have a smoking problem... \$\endgroup\$
    – richard1941
    Aug 30, 2019 at 15:22

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