DC-Transformer circuit help

  1. I recently learned that if you send direct current through the primary coil of a transformer, no power would be transferred to the secondary circuit? Why is that?
  2. jcsd
  3. Can you tell us why it works for AC? If so, then you should know why it does not work for DC.
  4. Theoretically, it would work. Since the flux in the core of the transformer increases by the integral of the applied voltage (Faraday's law), in an ideal transformer, the flux would just continue to increase. However, if you tried this with an actual transformer, you would drive the core into saturation and create a lot of heat.

    Dr. Frank Ferrese
  5. A Straight Answer:
    A changing current produces a changing magnetic field, which in turn can induce a current in the secondary. If the current is not changing, the magnetic field is not changing, so no current is induced in the secondary.

    When you first apply a DC voltage the current ramps up, so the field is changing and an initial current is induced in the secondary. But when the current stops changing (limited by resistance, for example) there will be no current induced into the secondary.
  6. dlgoff

    dlgoff 3,158
    Science Advisor
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