Magnetic fields within a toroid inductor.

[xee2]

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.

?? If you draw the line integral anywhere inside the toroid will it not always enclose the same amount of current?

[poynt99]

Yes. That was my point.

However, in a toroid, if you did have a very small Hall sensor that you could insert inside the toroid core at any radius, we would see a stronger reading at the inside radius vs. the outside radius.

[tinman]

Ok,i was refering to the cross section center of the core itself-not the air hole in the middle of the toroid.
So if the magnetic field is strongest within the core itself,why dont we put the secondary coil in the center of the core?,rather than around the outside with the primary winding, like a standard transformer. Dose anyone know what would happen with the secondary placed inside the core itself?. Would this reduce or remove any BackEMF that would effect the primary?.

There is another thing about the toroid coil that may answer another debate that was raised in another thread(MH will know this one im talking about) It is in reguards to this bloch wall claim.If it exist within a PM or EM,then it must exist in all PM's and EM's. So when we pass current through a toriod inductor,where exactly would this bloch wall be? Is the toroid the perfect example of magnetic fields looping around a magnet,without this bloch wall?

[MileHigh]

Xee2:

If your point is that the field is uniform inside the toroid

My point is that the field is not uniform inside the toroid.  The field inside the toroid is stronger the closer you go towards the center of the toroid.

For an infinitely long solendoid, the field is uniform inside the solendoid.

I agree, and that's a nice little thought experiment that proves that the field is uniform inside an infinitely long solenoid.  You just keep making the radius of the toroid larger and larger until you get a straight line.

Poynt:

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.

Yes but on the bench we normally work with toroids that are typically "doughnut sized" and the formula from the clip is relevant to bench work.

It also makes sense intuitively.  When you are hugging the inside wall of the toroidal cross section, the density of the wire loops per tangential centimeter is the highest.  So you would think that the magnetic field would be stronger where there is a higher wire loop density (as compared to the outside wall of the toroid where the wire loop density per tangential centimeter is lower.)

MileHigh

[poynt99]

Mags and tinman,

Forget about toroid coils for a moment, and consider this thought experiment.

If you had a very long solenoid coil, say 1" in diameter and 1 mile long, wound evenly along the entire length of the solenoid, and you energized the solenoid. Would you be able to detect any magnetic field anywhere around the solenoid, other than at the ends or within its core?

In other words, if you were standing 2640 feet from one end of the solenoid, and you had a Hall sensor with you, would you detect any magnetic field anywhere near the solenoid (assuming you could not probe inside it)?