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Why do transformers hum?

  1. Apr 8, 2009 #1
    Why do transformers hum? Is it the iron core vibrating & if it is what is it that makes it vibrate? Is it the little atomic magnetics in the iron changing directions with the ac? Can anyone enlighten me?
  2. jcsd
  3. Apr 8, 2009 #2
    Basically I think you are right,the coils carry a.c.and this results in the core going through many magnetic cycles per second.The changing magnetic flux then results in vibrations.
  4. Apr 8, 2009 #3
    Magnetostriction in the iron causes the iron laminations to change dimension when the excitation exceeds about 1 Tesla. Magnetostriction occurs twice per cycle, so the hum is 120 Hz (or 100 Hz) depending on where you live.
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