I have a 12mm long hard ferrite core that I want to use as an electromagnet. I have wound it with 0.8mm copper as tightly as I can by hand, in a single layer, but the field is not strong enough. I have placed another coil over that first coil, and then a third coil, each in parallel - branching before the core, and then re-connecting afterward - wound concentrically in the same direction, to increase the number of windings. I'm still not getting the magnetic force I need. The electrical source is a car battery with 490 cold cranking amps (CCA) -- There is no overheating now that I have 3 branches.

Am I doing something wrong? Is there a winding method that will work better? Do I need higher voltage or just higher current?

  • $\begingroup$ This may help you. $\endgroup$
    – user22180
    Jul 20, 2014 at 18:53
  • 1
    $\begingroup$ The question, while specific to an application of science, illustrates a fundamental physics misunderstanding and should remain open. $\endgroup$
    – user6972
    Jul 21, 2014 at 0:36

1 Answer 1


There are often material limits to how high the magnetic flux density can get. So no matter how much more current (not voltage) you apply you'll find the magnetic field stops increasing.

Notice how the curves start to flatten out for different materials (reference):


The relation between the magnetizing field H and the magnetic field B can also be expressed as the magnetic permeability: $\mu = B / H$ or the relative permeability $\mu_r = \mu/\mu_0$, where $\mu_0$ is the vacuum permeability. The permeability of ferromagnetic materials is not constant, but depends on H. In saturable materials the relative permeability increases with H to a maximum, then as it approaches saturation inverts and decreases toward one.

also see Saturation of an iron core?


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