magnetic flux question

Well, you *might* say it that way, but it's not quite correct. For one thing, it treats magnetic flux as something which "travels through" a medium, presumably in a manner similar to an electric current, and that's just not really so.

The difference between having a coil with a ferrite or iron core and one with an air core is the *permeability* of the core material. Technically, there are two "magnetic fields" covered by electromagnetic theory, known as the "B field" and the "H field," and the permeability of the medium is the relationship between these two. That by itself is about as clear as mud; another way to say it is that permeability is what determines how strongly magnetized a given material will be when a magnetic field is passing through it. (For instance, an air-core coil wth a given current might be a fairly weak magnet, but put an iron core into the same coil an pass the same current through it, and you get a much stronger magnet. The difference is the much greater permeability of the iron.)

Yet another way to look at this is that permeability is a hugely important factor in determining inductance, which is simply the ability to store energy in the form of a magnetic field (and is therefore analogous to capacitance, which has to do with the storage of energy in an electric field). If the magnetic field produced by a coil of wire is established within a material of high permeability (again, as in the case of an iron or ferrite core), you see a much greater inductance. (And so "permeability" has much the same role in inductors as "permittivity" - more commonly seen in the form of the "dielectric constant" - has in capacitors.)

Does any of that help?

Bob M.

Thanks for your answer. can you confirm the following then?

I always thought a b-field was magnetism and an a-field was the electro-field which traveled with the b-field (when applicable) but at right angles to it.

so then inductance is the storage of a b-field (magnetic "work") only, where capacitance is the storage of an a-field (electrical "work") only, correct?

and so a coil when charged/induced at its max is only storing a "magnetic potential", no electrical potential will exist at this time. when the magnetic field collapses back through the coil then a larger a-field will then be realized. right?

also, what is an h-field in common sense terms?

thanks.

Reluctance maybe what your looking for.

There is no field I've seen commonly referred to as the "a" field. The "magnetic" fields are commonly referred to as the "B" and "H" fields (again, related by the permeability of the material in which the fields are established), while the "electric" fields are the "E" and "D" (which are similarly related by the permittivity of the material). The classic "electric" and "magnetic" fields are the E and B, respectively, while the D and H are related to these but you don't really need to worry about them right now. If you get into a course on electromagnetic waves, etc., then you're going to get into the differences, but not until then.

More correctly, "inductance" is that property of a component or conductor whereby *energy* is stored in the form of a magnetic field, and "capacitance" is that property whereby energy is stored in an electric field.

I'm not sure what you're trying to say here, exactly, but let me take a whack at what I THINK it might be.

If you're running a direct current through an ideal coil (no resistance), then a magnetic field is created by the coil and there is a certain amount of energy in that field. There is no voltage drop ("electric potential") across the coil in this case, just a current through it. If, however, you attempt to change the current (including trying to shut it off), then energy comes back out of the field and creates a potential (voltage) across the coil in such a way as to oppose the change. (If, for instance, you try to open a switch which is carrying a sizable current through a large inductor, you can get a HUGE voltage and the switch will "arc over" as the inductor "tries" to maintain the current through it.)

This is where things get a bit complex. To a physicist, the B-field is the "magnetic field," while the H-field is the

*magnetizing* field; from an engineer, you'd commonly hear these called the "magnetic flux density" and the "magnetic field strength," respectively. About the best way I can show a "common sense" difference is to go back to an example I used in the last post - if you have an air-core coil you're trying to use as an electromagnet, you will find that that putting an iron core in increases the magnetic strength significantly. The B-field is the same in both cases, but the H-field has gone up with the iron core (due to the increased permeability).

Bob M.