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Induced EMF on a primary coil by a secondary coil

  1. Oct 8, 2009 #1
    1. Derive an equation to find the induced EMF on an inner solenoid by a changing current on an outer solenoid.

    2. Relevant equations
    We're given the equation EoRMS=(No*Ai*(2*pi*f)*(permeability constant)*IiRMS)/Li for the induced EMF on the outer solenoid by a changing current in the inner. I need an equation to replace this for when it's the other way around.

    3. The attempt at a solution
    I have no idea where to even begin, I just need a hint as to how I should start.
  2. jcsd
  3. Oct 9, 2009 #2

    Andrew Mason

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    Start with Faraday's law for a coil:

    [tex]V_{induced} = -N\frac{d\phi}{dt} = -NA\frac{dB}{dt} [/tex]

    where N is the number of coils in the inner coil, B is the magnetic field and A is the area enclosed by the coils.

    Can you apply Ampere's law to determine the relationship between the rate of change of current in the outer coil and dB/dt?

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