ampere-turns explaination?

jearls74

could someone please explain in simple terms what ampere-turns and ampere turns per meter means?

ctjen

Electromagnetism:

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.

Ampere-Turns:

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
as:
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
ampere-turns.

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.

Chris

jearls74

thanks chris, that explained it very clearly