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Experiment at home

  1. Sep 16, 2009 #1
    basic E and M from purcells:

    A change in magnetic field with respect to time, will induce a current in a conducting loop that is located in that changing magnetic field.

    Does that mean, that if I take a power cord that is plugged into a device while it is running, so that way it is taking a load, and wrap it into loops, that I now have a current loop alternating at 60 Hz, and therefore a varying magnetic field.

    With this magnetic field, could I stick in another wire loop inside and power a load?

    IE Lets say you wrapped the cord for your toaster oven around a metal jacket hanger. Would you be able to pull a current off of this hanger?
  2. jcsd
  3. Sep 16, 2009 #2


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    Gold Member

    No, because the power cord contains two (often twisted) wires. The same amount of current is flowing in (in the "hot" wire) and out of the device.
    Ideally the fields from the two currents cancel out meaning the net magnetic field is zero.
  4. Sep 16, 2009 #3
    So if I unraveled the power cord, I'd be able to perform this experiment?

    Also, since there is a load drawn from the device, let's say coffee maker, wouldn't that make the currents flowing in and out different? therefore having a net current? and net magnetic field?
  5. Sep 16, 2009 #4


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    Staff: Mentor

    Please don't start taking apart AC Mains power cords for experiments. You need a lot more knowledge and experience before you start messing with high voltages. The shock and fire hazards are just too great.

    Instead, get a 12Vac "wall wart" transformer power supply (like a charger from Radio Shack, etc.), and then you can start splitting the output wires apart to experiment with AC magnetic fields. Much safer!
  6. Sep 16, 2009 #5
    These are purely hypothetical questions
  7. Sep 16, 2009 #6
    I once bought a very long (I think 500 feet) coil of 14-Ga coiled copper wire (like contractors use for house wiring) and plugged it into the wall in series with a 1-KW kitchen appliance. Works nice. Lots of inductance.
  8. Sep 16, 2009 #7


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    Homework Helper

    Yes, that's exactly how the power adapters that convert AC to DC work: they have a step-down transformer that converts 120V to a lower AC voltage, which is then converted to DC with a rectifier circuit.
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