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Expert: Daniel Mazur - 11/24/2007


Question
Hi:

Dielectric strength and ohm [electric resistance] are electric entities. What are their magnetic equivalents?

Are there such things as "dimagnetic strength" and "magnetic resistance"? If so, what are they measured in?

Also, is there such a thing as "magnetic conductance" [like electric conductance]? If so, what is it measured in?


Thanks,

Green

Answer
Hello again,
according to Wikipedia: Dielectric strength of an insulating material = the maximum electric field strength that it can withstand intrinsically without breaking down, i.e., without experiencing failure of its insulating properties.
In magnetism we can only find a very vague analogy, I do not think it is a true one. In magnetic materials you have something called "coercive field", which for ferromagnetic compounds determines the field at which the magnetization will suddenly switch polarity. So, it is a threshold value to some process. However, it is not a breakdown in the dielectric sense, because there is no flow of any "charge" due to magnetic polarity switching. There may be a critical field of antiferromagnet transition to a ferromagnetic state, which may be an even better analogy, but I don't know, how strong an analogy you are looking for. The critical or coercive magnetic field would be measured in teslas or webers (there is some scatter in how people define these quantities) in the SI unit system.

For the "magnetic resistance" there is no analogy, because there are no magnetic charges (monopoles) and hence no flow of them. There is something called "magnetoresistance", which is however a name for the dependence of ordinary (!) electrical resistance on external magnetic fields. The same goes for "magnetic conductance" and "magnetoconductance".

Take care,
Daniel

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