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Factors that increase/decrease C-EMF

Discussion in 'General Electronics Discussion' started by Dretron, Mar 6, 2013.

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  1. Dretron


    Jun 9, 2012
    So when we have a magnet being moved by an electromagnet. And the magnet is being rotated, constantly passing the electromagnet(Pretty much like a motor.)
    And the input EMF is being resisted by the C-EMF generated by that motion of the magnet
    (If there are other reasons why C-EMF is generated besides the one I mentioned please do share)

    Now what factors would cause that C-EMF to decrease.
    And what factors cause it to increase?

    When we mean by change in magnetic field, what is ment exactly? The force,the flux lines?!?!

    Thank you.
  2. BobK


    Jan 5, 2010
    Back EMF is dependent on the load. The larger the load the larger the back EMF.

    If you are thinking about how to reduce it to get better efficiency forget it. It is basic physics: conservation of energy. If there were no back EMF when you spun a generator, you could spin it with no effort, getting free energy (well, except for the friction, which would not increase with the load)

  3. Dretron


    Jun 9, 2012
    The faster the motor is... The more C-EMF is generated.
    What more examples can be given other than that?

    And if C-EMF is increased. The supplied power source will increase current? To resist C-EMF?
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    When current is induced to flow in a wire (by virtue of it passing through a magnetic field), that current produces its own magnetic field which opposes the wire's movement through the magnetic field that is inducing the current.

    If the first magnetic field is being generated by an electromagnet, The induced magnetic field in the conductor is now crossing the conductors in the electromagnet, attempting to induce a current in the reverse direction to the current flow. Since current can't flow both ways, the effect is seen as something like a back pressure. It appears to be a voltage operating in opposition to the voltage placed across the electromagnet coil.

    To maintain the current, the voltage across the electromagnet's coil must increase by the exact value of the counter-emf.
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