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Dc supply to transformer

  1. Dec 23, 2014 #1
    my friend gave a dc supply to a transformer in my college lab accidentally and the fuse went off can i get an explanation on why this happened?
  2. jcsd
  3. Dec 23, 2014 #2
    Transformer work only with AC voltage. For DC transformer act just like a short wire (a very small resistance ).
  4. Dec 23, 2014 #3
    Can you please explain how a transformer shows very small resistance to a DC supply?
    Last edited by a moderator: Dec 23, 2014
  5. Dec 23, 2014 #4


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    Actually this sounds like a disguised homework question. If you are messing with transformers in lab you should already know the answer to the question.
  6. Dec 23, 2014 #5
    Because transformers is essentially just two or more coils of wire wrapped around the core. And wires has "low" resistance.
  7. Dec 23, 2014 #6
    You have a careful smart friend
  8. Dec 23, 2014 #7


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    Actually, if your friend had been able to measure the way the current varied around the time of switch on, he would have found that the current value followed a curve, because the Iron core of the transformer behaves like an electromagnet. The magnetic field energy takes time to build up and it produces a 'back emf' which delays the DC current increase (This would be fairly quick with a mains transformer - only a few tens of milliseconds before the fuse started to blow.)
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