# Why Coils?

## Main Question or Discussion Point

hey everyone, I have a questions, that is very general, and perhaps, silly... but why are coils so significant in terms of electricity and magnetic fields? why is it when you push a magnet through a coil, you get a charge, but not when you touch it to a straight copper pipe? Or when you see generators, they always use the coil form? What is it about a metal coil, that conducts better than any other shape?

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phinds
Gold Member
2019 Award
Coils don't conduct better than other shapes they just make use of inductance in a way that straight wires don't. This is really basic electronics and you'd learn more by studying it that getting a simple answer here.

I Googled "inductance in coils" and got a zillion hits.

meBigGuy
Gold Member
Basically through inductance, capacitance, and resistance we can build circuits that are frequency selective. For example, read about resonance. Coils have inductance, which is what is special. Of course frequency selectivity is but one of the applications of circuits containing coils.

Another simple answer or point, other than it not being about conducting, is that current flowing in the coil creates a magnetic field, and the strength of the field is proportional to the ampere-turns. So a stronger coil needs more current or more turns of the wire.

Integral
Staff Emeritus
Gold Member
I would say that the difference between a coil and a straight wire is that the coil interacts with itself, that is the field by generated by a given bit of wire is felt by other nearby bits of wire. The field generated by a straight wire does not cross the wire again.

It depends on the shape of the magnetic field you want to generate.

When current passes through a wire, it creates magnetic field that is circular around the wire.

While if you turn it in the shape of the coil as you mentioned you will get magnetic field in the shape of approximately straight lines which can be more easily manipulated for your application purpose.

In motors applications, the torque generated by 3 phase motor is the result of the cross product of magnetic field from stator and rotor, so if you have 2 straight magnetic fields you can easily find the torque resulted from the interaction of these 2 fields.