Magnetism is a class of physical phenomena that includes forces
exerted by magnets on other magnets. It has its origin in electric currents and
the fundamental magnetic moments of elementary particles.
Now we answer the question what is magnetism? Magnetism is the force by which
the objects are attracted or repelled by one another. Usually these objects are
metals such as iron. Besides iron, other materials that are easily magnetized when
placed in a magnetic field include nickel and cobalt. Magnetism is a force of attraction
or repulsion that acts at a distance. It is due to a magnetic field, which is caused
by moving electrically charged particles. Iron is not the only material that is
easily magnetized when placed in a magnetic field; others include nickel and cobalt.
Magnets can also be formed and such magnets are called electromagnets. A simple
electromagnet is formed with a battery and copper wire coiled around a metal rod
such as a nail. There is evidence that there is an electrical basis for magnetism.
Pierre de Mari court checked angles pointed out by an iron rod placed at
various points of a natural magnet. He found that the directions were in such a
way that they rounded the sphere and passed through two points diagonally opposite,
which he called the ends or poles of the magnet. Later experiments showed
that every magnet, regardless of its shape, has two poles, called north and south
poles, that exert repulsive as well as attractive forces on other magnetic poles
just as electric charges exert forces on one another.
Later William Gilbert extended de Mari court’s experiments to a variety of materials.
Using the fact that a iron rod orients in some preferred directions, as per his
hypothesis Earth itself is a large permanent magnet. Further a Torsion Balance was
used for experiments and it was postulated that the force exerted varies inversely
with the square of distance between them.
Magnetic Poles, Forces, and Fields
Magnetic Poles: Every magnet has two poles. The poles are the
points in a magnet where the magnetic strength is at its peak. These poles are called
the north and the south poles or the north seeking and south seeking poles. When
a magnet is suspended or hung somewhere the magnet lines up in a north - south direction.
As we know that the like charges repel and the unlike charges attract, so when the
North Pole of one magnet is kept close to the north pole of another magnet, the
poles are repelled. When the south poles of two magnets are placed near one another,
they also are repelled from one another. When the north and south poles of two magnets
are placed near one another, they attract each other.
The attraction or repulsion of two magnets towards one another depends on how
close they are to each other and how strong the magnetic force is within the magnet.
The further apart of the magnets are the less they are attracted or repelled to
Note: Even when a magnet is broken into pieces each broken piece
has its own north and South Pole.
Magnetic Field: The imaginary lines of flux originating from
moving or spinning electrically charged particles constitute the magnetic field.
For example the spin of a proton and the motion of electrons through a wire in an
electric circuit constitute magnetic fields. It is undoubtedly a special property
of space. All materials are influenced to some extent by a magnetic field. Most
materials do not have permanent moments. Some are attracted to a magnetic field,
others are repulsed by a magnetic field while others have a much more complex relationship
with an applied magnetic field. Substances that are negligibly affected by magnetic
fields are known as non-magnetic substances. They include copper, aluminium,
gases and plastic. Even pure oxygen exhibits magnetic properties when cooled to
a liquid state.
The magnetic field of an object can create a magnetic force on other objects with
magnetic fields. When a magnetic field is applied to a moving electric charge, such
as a moving proton or the electrical current in a wire, the force on the charge
is called a Lorentz force.
When two magnets or magnetic objects are close to each other, there is a force
that attracts the poles together. Attraction always occurs between unlike poles.
Except iron, magnets also attract nickel and cobalt.
When two magnetic objects have like poles facing each other, the magnetic force
pushes them apart. Magnets might also repel diamagnetic materials
Magnetic and electric fields
There is a close relation between the magnetic and electric fields. They are similar
as well as different.
Electric charges and magnetism similar
The poles of a magnet behave in the same way as the electric charges. The positive
(+) and the negative (-) electrical charges attract each other and so do the North
and the South Poles in a magnet. In electricity like charges repel, and in magnetism
like poles repel.
Electric charges and magnetism different
The magnetic field is a dipole field as every magnet has exactly two poles. But
in electricity, a positive (+) or a negative (-) charge can exist independently.
Electrical charges are called monopoles, since they can exist without the opposite
charge but a single magnetic pole can never be isolated.