Electronic – What would be the difference in a coil of wire and just a cylinder of solid copper


Ok so I am learning about induction and I always see coils of wire with no insulator. So I was wondering, What is the significance of it being a coil of wire rather than just a solid cylinder since there are already many points of contact between each "wrap" of the coil?

Best Answer

The part you are missing is that what looks like uninsulated wire actually isn't. A lot of enamel coated or "magnet wire" can look like bare copper at first glance, but the wire is actually coated with a thin semi-transparent insulation layer. The reason for using thin insulation is so that lots of turns of the coil can fit into the tightest possible space.

Electrically, a coil of wire is quite different from a cylinder. To make a magnetic field, you need current flowing around where you want the field. Think of a cylinder of current surrounding the area. The magnetic field is proportional to the total current in the cylinder.

A coil is sortof a cheat on that. The same current is re-used each turn to add to the apparent cylinder current. Let's say you have a coil with 100 turns. If you run 1 A thru it, each of those turns contributes 1 A to the overall cylinder current. You get the same magnetic field as if it were a solid cylinder with 100 A running around it.