An electromagnetic force is a force that acts on a conductor when current flows in the conductor within a magnetic field. It is utilised to operate starter and wiper motors, and the pointers of ammeters, voltmeters, etc.
DIRECTION OF ELECTROMAGNETIC FORCE
Let’s assume the N and S poles of a magnet are placed near other, and a conductor is put between them, as shown. Then current is applied to the conductor.
The
following can be said about the magnetic flux created in this case: There are a
smaller number of magnetic lines of force above the conductor since the
direction of the magnetic fluxes created by the magnet and the direction of
those created by current oppose each other. In contrast, there are a larger
number of magnetic lines of force under the conductor as their directions
coincide.
Since
magnetic lines of force act similarly to stretched rubber bands in many ways,
the magnetic lines of force attempt to become straight. This tendency is
stronger under the conductor than above it. Therefore, a force is generated
that tends to push the conductor upward. This force (F) is called an
electromagnetic force.
The
direction of an electromagnetic force can be determined from Fleming’s
left-hand rule.
STRENGTH OF ELECTROMAGNETIC FORCE
Strength F
of an electromagnetic force varies in proportion to density B of the magnetic
flux (the number of magnetic lines of force per unit area), current flowing l
in the conductor, and length L of the conductor, as expressed below:
F = B x I x L
In other words, an electromagnetic
force is greater when there is a stronger magnetic field, when more current flows
in the conductor, or when the length of the conductor within the magnetic field
is greater.
