(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

This is more of a general question about magnetic flux in a uniform magnetic field, but I think this is the correct place to post it.

I understand that magnetic flux through an area A is the product of the magnetic flux density B and the projection of area A onto a surface perpendicular to the field.

What I don't understand is the way it works for a coil of wire, say just one loop lying perpendicular to the field. I don't understand why you take the area as being the area of the physical circle created by the loop - i.e. pi*r^{2}where r is the radius of the circle created by the loop. Surely it should be just the area of the wire?

2. Relevant equations

φ = BAcosθ

(which becomes φ = BA for this example)

3. The attempt at a solution

If you take a straight wire, the area you take would be the length of the wire times the diameter. So why is it that when you coil that wire around the flux changes because you apparantly take the area of the circle it describes? How does the empty space in the middle of the coil cut any of the field?

Perhaps I am understanding magnetic flux wrong entirely?

Any help would be appreciated.

-Confused A-level student

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# Problem with calculating magnetic flux for a single coil of wire.

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