When creating a simple electromagnet, all you need is a nail and some copper wire, and a battery. I did this using non-coated copper wire, and after thinking about it for a bit, I was confused as to why it was working. Theoretically, the current moving through the coil around the nail should induce a strong magnetic field concentrated in the center of the coil (in the nail). However, if this wire is not coated, wouldn't the current simply "jump" between coils rather than following the spiral pattern around? And since it is no longer moving in a coil path, wouldn't it fail to create an electromagnet? Yet still, the electromagnet was able to pick up several paperclips with only about 20 coils around the wire.

  • \$\begingroup\$ I should add that I tried picking up paperclips with the nail without current just to see if it was slightly magnetized, and it was not. \$\endgroup\$ – vcapra1 Jun 10 '18 at 18:00
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    \$\begingroup\$ Almost certainly you are using coated wire then. \$\endgroup\$ – Andy aka Jun 10 '18 at 18:04
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    \$\begingroup\$ Bare copper forms an oxide crust quickly enough in air, even if you don't see it by eye. It's called 'patina.' Given enough time, you can see it, though. Anyway, this detail plus your nail's surface, which has its own modest coating of some kind, probably account for a good part of your success. It's likely the case that the copper itself remained far, far more conductive. But I can't say for sure. (You could attempt the same experiment after using steel wool on the nail and copper surface. Or just wind really tightly to see if that changes things.) \$\endgroup\$ – jonk Jun 10 '18 at 18:04
  • \$\begingroup\$ Paper clips weigh less than the wire. If you want more force, consider high relative mu metal forms with Teflon tape and magnet wire. \$\endgroup\$ – Tony Stewart EE75 Jun 10 '18 at 18:28

Your bare copper wire probably has some tarnish (a.k.a some oxidation) and oil on it that may allow some of the coil turns to act like an inductor instead of being a total short.

You are on the right track though of realizing that you would not normally make an electromagnet coil out of bare copper wire. Normally enamel coated wire is used for coils because it insulates the turns but is still thin. The thin coating allows the wire turns to be packed more tightly on the coil resulting in more total turns in a given space. If you even tried to make a coil with wire insulated with thick plastic, PVC or Teflon insulation you would note the difference in the performance of the electromagnet right away.

  • \$\begingroup\$ You may want more torque with high permeality \$\endgroup\$ – Tony Stewart EE75 Jun 10 '18 at 18:15
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    \$\begingroup\$ Thanks, wrapping the coils tighter caused it to not work at all. This is what I was expecting, I just thought that the tightness I had before would already be enough for it to short circuit and have no effect. Thanks for your answer! \$\endgroup\$ – vcapra1 Jun 10 '18 at 18:21

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