Magnetic Field
Whenever a current flows through
a conductor, a magnetic field is
established around that conductor.
the cross-sectional
views of two conductors carrying
current in opposite directions. The
cross sign (¥) shown inside the
conductor indicates that current is
entering the conductor whereas the
dot sign (◊) shown indicates that the
current is coming out in a direction
perpendicular to the plane of the paper. Directions of flux lines around the conductors
are also shown in the figure. The direction of the lines of force around a conductor
is readily determined by the right-hand rule which is as follows—point the thumb
of the right hand in the direction of the current in the conductor and wrap the fingers
of the right hand around the conductor. The finger tips will point in the direction of
the lines of force.
The cork screw rule can also be applied to determine the direction of the lines of
force around a current-carrying conductor.
Concentration of flux can be produced by causing the current to flow through
a coil instead of through a conductor. Inside the coil the flux contributed by each
segment of the coil is in the same direction. Thus a strong magnetic field is produced
due to current fl owing through a coil. The introduction of a
magnetic material as a core for the coil increases the flux. A simple right-hand rule
indicates the direction of magnetic flux inside a coil: Wrap the fingers of the right
hand around the coil, with the finger tips pointing in the direction of the current, the
thumb points in the direction of the magnetic flux.
