Just
as an electric current cannot flow in an electric circuit until we connect it
to a voltage source, magnetic flux (magnetic line of force) cannot be
established until a magnetomotive force is produced.
as an electric current cannot flow in an electric circuit until we connect it
to a voltage source, magnetic flux (magnetic line of force) cannot be
established until a magnetomotive force is produced.
Magnetomotive
force in a magnetic circuit is the counterpart of electromotive force in a
electric circuit.
force in a magnetic circuit is the counterpart of electromotive force in a
electric circuit.
In an
electromagnet, magnetic flux appear only when electric current flows in a
solenoid. Therefore magnetomotive force (mmf) must be a direct result of
electric current. We can therefore establish a unit of mmf on the basis of the
electric current in a single-turn coil of a wire.
electromagnet, magnetic flux appear only when electric current flows in a
solenoid. Therefore magnetomotive force (mmf) must be a direct result of
electric current. We can therefore establish a unit of mmf on the basis of the
electric current in a single-turn coil of a wire.
Hence,
the ampere is the SI unit of magnetomotive force. Since adding turns of wire to
a solenoid produces the same effect as adding an extra strand to a single-turn
coil, each strand carrying the input current to the coil, the effective ampere
of magnetomotive force is the product of the coil current and the number of
turns in the coil.
the ampere is the SI unit of magnetomotive force. Since adding turns of wire to
a solenoid produces the same effect as adding an extra strand to a single-turn
coil, each strand carrying the input current to the coil, the effective ampere
of magnetomotive force is the product of the coil current and the number of
turns in the coil.
The
letter symbol for magnetomotive force is Fm.
letter symbol for magnetomotive force is Fm.
Fm
= NI
= NI
Where
N is the number of turns in the coil, I, is the actual current flowing through the coil and Fm is
the magnetomotive force in ampere (efective).
N is the number of turns in the coil, I, is the actual current flowing through the coil and Fm is
the magnetomotive force in ampere (efective).
So
that we do not forget that the total magnetomotive force is the product of
actual coil current and the number of turns of wire in the coil. We can say
that the ampere-turn is the practical unit of magnetomotive force.
that we do not forget that the total magnetomotive force is the product of
actual coil current and the number of turns of wire in the coil. We can say
that the ampere-turn is the practical unit of magnetomotive force.
