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Thread: ElectroMagnetic field strength exiting conductor ?

  1. #1 ElectroMagnetic field strength exiting conductor ? 
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    Does the strength of a electromagnetic field diminish after exiting a conductive material such as copper. If so, would this be from the field transferring some of its energy to the electrons within the conductive material...?


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    Forum Cosmic Wizard
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    You mean like a radiowave getting received by an antenna?


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  4. #3  
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    Quote Originally Posted by dan hunter View Post
    You mean like a radiowave getting received by an antenna?

    No. I mean when electromagnetic fields 'cut' through a conductive material for example..electromagnetic induction
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  5. #4  
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    It is the same thing really.

    The short answer is yes. It gets a bit more complicated when you start calculating the load on the circuit.
    In an electric motor that is spinning freely there is a back emf generated that increases the resistance of the field windings and reduces the current through them.
    Under load the motor is slowed and the field windings draw more current, in other words more power.
    One way this appears is torque produced by the motor but it also causes heating of the motor.
    Overloading a motor and stopping the fields from rotating, or running it at to low of a voltage, will create an excessive current draw and burn out the motor.

    Antennas do much the same thing, An unloaded antenna returns almost all of the energy to the radio wave as it passes, but if the antenna is powering a radio circuit it is drawing power. The transmitter stations can see this as a load too and draw more current because of it.

    I am not a radio guy or motorman though so hopefully somebody with more background can give you a more complete answer.
    Last edited by dan hunter; August 16th, 2014 at 12:13 PM.
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