If you had a design for an electromagnet core that required it to be assembled out of several parts would it still produce as strong a magnetic field as the same core but made out of a single piece?
My thinking is that the magnetisation may not be as effective across the boundary between two metal components that are touching as opposed to a solid piece of metal but I am unsure as to how detrimental that would actually be.
Hi Thomas Harry Scone ,
the basic equation for the relation between the current I, the number N of windings of wire in the coil, the magnetic field H in and the length d of different sections of the core resp. of air gaps in the core is:
I * N = H1 * d1 + H2 * d2 + ...
where all sections form a closed path for the magnetic field.
In sections filled with ferromagnetic metal, the order of magnitude of H will be 103 A/m, in sections filled with non-ferromagnetic matter, H = B / my0, which results in about 106 A/m for common values of B. So, air gaps increase the "magnetic resistance" considerably, unless d -> 0.
If the assembled parts fit together perfectly, or, to put it another way, if the weight of the assembled core is not less than the weight of a one-piece-core of exactly the same dimensions (made from the same material, of course), than the magnetic field will be the same.
In transformers, we often have a core composed of two pieces (e.g. E - I core) in order to facilitate the winding and assembling of the coil, and for all practical purpuses, the calculation of the effect of the core is the same as for a one piece core, provided that the touching surfaces fit together very well.
The gap has to be small though, because any air gap has reluctance hundreds of times (relative magnetic permeability) larger than core material of the same size.
the magnetic permeability of the air influences, so the field intensity will be better if there is no air involved
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