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Ampere-turns explaination?

  1. Apr 13, 2008 #1
    could someone please explain in simple terms what ampere-turns and ampere turns per meter means?
  2. jcsd
  3. Apr 14, 2008 #2

    It has been found that an electric current sets up a magnetic field
    similar to that produced by a permanent magnet. This action is known as
    Electromagnetism and is very important in many devices. A desirable
    feature of electromagnetism is that it is possible to control the strength
    and polarity of the magnetic field. When current exists in a coil, the coil
    has all the magnetic qualities of a permanent magnet and is called an
    Electromagnet. If this electromagnet is brought near a permanent
    magnet or another electromagnet, the like and unlike poles react exactly
    as explained for the permanent magnets. Moreover, an increase of current
    in the coil increases the strength of the magnetic field, and a decrease
    of current weakens the field.


    When the number of loops or turns of the coil is increased and the
    current remains the same, the strength of the magnetic field increases.
    Each loop or turn of the coil sets up it's own magnetic field, which unites
    with the fields of the other loops to produce the field around the entire
    coil. The more loops, the more magnetic fields unite and reinforce each other
    and, as a result, the total magnetic field becomes stronger.

    To compare the magnetic strength of different coils, and to obtain
    a basis for measuring the magnetomotive force of an electromagnet, the number
    of turns of wire is multiplied by the number of amperes of current carried
    by the wire and the result is called Ampere-Turns (NI). The ampere-turn
    is the unit for measuring the magnetomotive force of a current-carrying
    coil. In a formula, the magnetomotive force in ampere-turns can be expressed
    F = NI
    F = magnetomotive force in ampere-turns
    N = number of turns
    I = current in amperes
    For example:
    A coil with 10 turns and a current of 10 amperes has an F of 100

    The above excerpted from: http://ourworld.compuserve.com/homepages/boyce_smith/magnets.htm

    Ampere-turns per meter is just as it reads, the number of ampere turns per length of the electromagnetic coil.

  4. Apr 15, 2008 #3
    very good explanation

    thanks chris, that explained it very clearly
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