In reference to the Power losses in a Transformer, the author of Physics Textbook writes:

As a result of magnetic hysteresis, the magnetic energy stored in the magnetic field as the magnitude of the field increases is not all given back as the field magnitude decreases, resulting in power lost.

I am having difficulty in understanding the meaning of these lines. As far as I understand,due to magnetic hysteresis, energy is lost as the magnitude of magnetic energy changes. Is this understanding correct?

  • $\begingroup$ Atoms wiggle and that takes energy, which dissipates as heat. $\endgroup$
    – user56903
    Apr 3, 2016 at 15:13
  • $\begingroup$ There is a good explanation here $\endgroup$ Mar 29, 2018 at 7:49
  • $\begingroup$ As a note, the heat produced in one cycle is directly proportional to the area of the loop $\endgroup$
    – user600016
    Sep 26, 2019 at 7:40

1 Answer 1


In an AC (alternating current) transformer the magnetic field changes polarity, which in turn induces AC currents in the secondary loop of transformer. AC current in primary loop flows in a cycle, during the first half of this cycle the magnetic field is in a specific direction, and during the second half the field has to be in opposite direction. If during the first half of the the cycle the resulting magnetic field causes magnetic hysteresis in the transformer core, during the second half of the AC cycle this magnetic hysteresis is opposite the magnetic field resulting from second half of AC cycle. The second half of AC cycle has to remove the hysteresis from the first cycle to induce a strong field in magnetic core of the transformer. Of course, the second loop generates its own hysteresis again, which has to be removed by first half of next cycle of AC current, resulting in further power loss.


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