# Irregular shaped coil in electromagnetism

#### pjreijiri

Joined Aug 19, 2015
101
hello everyone,

I have a question about electromagnetism.
If we have a magnet and we moved it “in” and “out” of a non-circular shaped coil, would it still create the same current/voltage?
and if we have more than 1 magnet (all faced in the same direction) how would that affect the current and voltage?
You can check the attached picture for a more clear representation.

Regards

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#### AlbertHall

Joined Jun 4, 2014
12,328
If a wire is in a changing magnetic field then a current will be induced in that wire.
Multiple magnets with the same polarity inside the coil will increase the effective magnetic field.

#### pjreijiri

Joined Aug 19, 2015
101
So the shape of the cross section of the coil is not a problem.
Is there a different way in getting the voltage and current across and through the coil than the circular coil?

Thank you

#### AlbertHall

Joined Jun 4, 2014
12,328
Is there a different way in getting the voltage and current across and through the coil than the circular coil?
I don't understand what you are asking here. Connection of a voltmeter and/or ammeter does not depend on the shape of the coil though the voltage and current will probably vary depending on the shape and how it relates to the magnetic field.

#### DGElder

Joined Apr 3, 2016
351
In a uniform magnetic field the voltage induced in a closed loop is proportional to the rate of change in the cross sectional area of the loop perpendicular to the magnetic field. The shape doesn't matter. Look up Faraday's Law.

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#### AlbertHall

Joined Jun 4, 2014
12,328
Except the field will not be uniform.

#### pjreijiri

Joined Aug 19, 2015
101
Do you think, I make an assumption of turning the area to a circle and multiply the flux generated by one magnet by the number of magnets that I have?
At least to get a feel of where to start

#### DGElder

Joined Apr 3, 2016
351
Probably, but since we have no context or specifics for these questions it just looks like another XY problem.

http://xyproblem.info/

#### pjreijiri

Joined Aug 19, 2015
101
I have a shape similar to the onei attached earlier. It has 7 magnets each are N45 30mm diameter and 4mm thickness. The area of the loop is around 0.02m2 and the magnets are around 21mm from the edge

#### wayneh

Joined Sep 9, 2010
17,493
What's missing, if you want a quantitative answer, is the geometry of the field lines and the strength of those lines. Magnetic field lines are a bit like a circuit, in that they have to form a closed loop to the other pole of the magnet. If they make a big arc through air or vacuum (both of which have very low permeability), the situation is very different than if they are attached to a steel structure (which has a high permeability) that nearly closes the circle and tightens any air gap. The field lines cutting through the loop would be much stronger in that latter case.

This all said, it can be very difficult to make quantitative predictions involving magnets. A little experimental data may be far more useful.