# Homework Help: Square toriods vs. circula toroids

1. Oct 26, 2007

### blindnz

1. The problem statement, all variables and given/known data
Just a question when determing the B-field inside the volume of a toroid as a function of its radius.
Does it change the problem if the toroid has a non circular cross section i.e a square rather then a circle?

2. Oct 27, 2007

### qspeechc

No. Do the electromagnetic laws say anything about the shape? Only about the space of the area or volume you choose, nothing about what the current is doing inside or outside that.

3. Oct 27, 2007

### Shooting Star

Do you mean a toroid around which a wire is wound?

If so, then the cross-section has to be the same all along. The shape does not matter. Also, the wire has to be tightly wound, i.e., very less gap between the turns.

If the question pertained to something else, then just ignore all this.

4. Nov 15, 2011

### MATHLETE1

When you say that the square toroid will have the same calculation for the B-field as a circular one do you mean that it will depend on the radius or would it depend on the width of the rectangular cross section. Such as if the cross sectional dimensions were of height of a and length of b the B-field would be:

∫B(dA)= μNI → B∫(dA)=μNI → B(ab)=μNI → B=μNI/(ab) where B is dependent on b.

Or do you mean that B=μNI/(2piR)?