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Electromagnetism issues need clearing up

  1. Nov 27, 2006 #1
    In electromagnetism, when there is an emf is induced in a secondary coil from a current flowing in a nearby primary coil (such as in a transformer), then how is the mutual inductance, number of turns of each coil, the current in the primary coil, and the emf in the secondary coil related?

    From the reading that I have been doing, I think that for a single coil:
    [tex] B = \frac{u_0NI}{2 \pi r} [/tex]
    Where the [itex]u_0[/itex] is the permeability of free space (I don't know how to get the proper symbol), [itex]N[/itex] is the number of turns, and [itex]B[/itex] is the magnetic field strength.

    From what I have gathered from the reading, is:
    [tex]E = -\frac{d \psi}{dt} = -L \frac{dI}{dt} [/tex]
    Where I have used [itex]E[/itex] for emf, and psi for the flux (I don't know how to get the convention symbol), and [itex]L[/itex] is the inductance of the secondary coil, however, I am unsure as to how the mutual inductance (M) is related to the inductance (L).

    I think the problem is that when people speak of inductance, I am unsure what they mean the inductance of.

    The reason why I am asking is that I have a question which uses this idea, but I am so close to getting it, that I would rather not post the problem in the homework section.

    Thanks in advance.
     
    Last edited: Nov 27, 2006
  2. jcsd
  3. Nov 27, 2006 #2

    Andrew Mason

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    L, self inductance, is the ratio of induced emf in an inductor (coil) to rate of change of current in that inductor: Emf = L dI/dt

    Mutual inductance relates to two coils in which a change of current in one coil induces an emf in the other. Emf = MdI/dt where Emf is the emf in the other coil.

    AM
     
  4. Nov 27, 2006 #3
    [itex]\phi [/itex]?
     
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