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Inductive interference from two EM coils (aka a transformer)

  1. Apr 17, 2010 #1
    I've been wondering about this for a long time.

    The little black box that you plug into the wall so you can power your electronic devices contains a general run-of-the-mill transformer.

    But if the power is completely shut off to the device: not draining any current waiting for a power button to be pressed, or even unplugged from the device end so the cord is left dangling; then shouldn't the power consumption from the source (the power company's electric meter) be the same as if it were drawing the maximum that this device possibly could?

    The source coil in the transformer is a simple inductor. It provides a load (resistance from the coil) which is converted to (marginal) heat and a magnetic field. The other coil induces an electric current (and a bit more heat) from the alternating magnetic field.

    Whether or not that other coil uses that induced current shouldn't affect the current drained from the source, right? I mean the entire circuit of the device could be replaced with a theoretical metal plate representing the resistance of the entire circtuit (reactance and impedance not applying after AC->DC conversion takes place). Now, I don't see how drain to source inductance can make any printed circuit or conglomerate of wires or whatever induce a voltage in the source and stop the source coil from being a straight (-) ---v^v^--- (+) circuit. (that's a resitor)

    So there's really no point in turning my laptop computer off, right?
    Last edited: Apr 17, 2010
  2. jcsd
  3. Apr 17, 2010 #2
    That doesn't help at all.
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