Magnetic fields within a toroid inductor.

[Dave45]

The magnetic field is strongest closest to the center (see pic) but the magnetic field is contained and really is of no concern other than using it to control the electric field.

[poynt99]

Xee2:

Unfortunately that's not correct.  Please have a look at the clip I linked to again:

http://www.youtube.com/watch?v=pCSHcftPAIM

MileHigh

MH,

xee2 is correct. He is referring to the cross-section of the toroid "tube", not the doughnut hole of the toroid.

[MileHigh]

Poynt:

He is referring to the cross-section of the toroid "tube", not the doughnut hole of the toroid.

I know that he is referring to the cross-section of the tube.  The magnetic field is strongest inside the toroid tube along a circle whose points are hugging the inside wall (closest to the center of the doughnut) of the cross-section of the toroid.

B = u₀*N*I/2*Pi*r

The magnetic field strength inside a toroid (center of toroid when sliced like a bagel) is proportional to the number of turns and the current, and inversely proportional to the distance from the center of the doughnut.

The above formula is for an air core.  For the case when there is a ferromagnetic core, just multiply it by the relative permeability of the core material.

MileHigh

[xee2]

Xee2:

Unfortunately that's not correct.  Please have a look at the clip I linked to again:

http://www.youtube.com/watch?v=pCSHcftPAIM

MileHigh

If your point is that the field is uniform inside the toroid, I agree. I was trying to show that it was centered inside of the toroid and got sloppy. For an infinitely long solendoid, the field is uniform inside the solendoid. And, since a toroid is like a solelnoid bent into a circle, the toroid is like an infinitely long solenoid since it has no ends. Therefore, the field inside the toroid is uniform and is not stronger at center than at edges. Is that what you were pointing out? Is there something else that was wrong?

[poynt99]

That's true. However, the "dl" factor tells us that the integral of B around the full  toroid loop should be the same within the inner and outer radius.

If the radius of the toroid is >> than the radius of the cross-section, then the B-field intensity inside the toroid core will, for practical purposes be constant from the inner to outer radius.