# B Magnetic field of a circular electromagnet?

1. May 13, 2018

### kolleamm

I know that the poles of an electromagnet that is straight is at the ends but what if the metal core is an iron ring?

2. May 13, 2018

### Staff: Mentor

Then you have a circular magnetic field. This is called a toroid magnet, and you'll find it in various particle detectors, fusion reactors and probably a couple of other places.

3. May 14, 2018 at 1:14 AM

### kolleamm

Would the poles be perpendicular to the ring's plane?

4. May 14, 2018 at 2:14 AM

### Staff: Mentor

There are no magnet poles in this case.

5. May 14, 2018 at 6:18 AM

### Staff: Mentor

Hints: what does it mean for part of a magnet or electromagnet to be a "pole"? Does that condition hold for any part of a toroid?

6. May 15, 2018 at 2:21 AM

### kolleamm

It would mean that it could attract/repel other magnets right?

Would such a toroid electromagnet be able to repel or attract though? I had this idea of where I could make two of these toroid electromagnets repel and attract each other perpendicular to their plane, if that's possible.

7. May 15, 2018 at 5:45 AM

### Staff: Mentor

Outside you have a bit of stray field, which can lead to a weak force. Inside the field is quite homogeneous, so you don't have a net force. You can have torque - the magnet trying to align itself with the magnetic field.

8. May 15, 2018 at 6:44 AM

### Staff: Mentor

And what is it about the magnetic field configuration (near the poles) that causes it to attract/repel other magnets? To keep things simple, suppose the "other magnets" are small (in physical size) compared to the magnet in question.

Also, by "attract" I don't mean just that the "other magnets" rotate to align themselves with the field. I mean that there is a net force which attracts them to or repels them from the magnet in question.