By Prof. Liwayway Memije-Cruz

 Magnetism is a phenomenon of
physical science that arises due
to the forces between objects
brought about by the motion of
electrical charges within those
objects.
 The motion of electric charges
creates a magnetic field, which
exerts a magnetic force on
charged particles that move
within that field.
 A magnetic field flows from one
end of an object to the other,
creating a dipole with positive
and negative ends.

 All magnets have
two types of
poles: north-
seeking poles or
north poles and
south-seeking
poles or south
poles.

 The magnetic
strength is the
strongest at
the poles of
the magnet.

 Both Earth’s inner and outer
core are metal, but the outer
core remains liquid while
pressure keeps the inner core
solid. The liquid outer core is
constantly moving. This
moving metal generates a
magnetic field around the
planet. This magnetic field
makes a compass point to
north or south. It also
protects the planet from the
Sun’s harmful rays.

 Heat and the Earth’s spin keep the outer
core moving. This movement causes
electrical currents in the core, which is
mostly iron. The electrical currents create
a magnetic field that extends into space.
 The magnetic field is tilted slightly from
the Earth’s axis.
 Sometimes the magnetic field is stronger
than at other times. Sometimes the
magnetic field’s alignment moves from
the Earth’s spin axis. The magnetic North
Pole keeps moving. Right now, the
magnetic North Pole is very close to the
Earth’s axis. One hundred years ago, it
was in Arctic Canada.
 The magnetic South Pole also moves.
 The magnetosphere is the magnetic force
that extends into space. This force acts
like a shield, protecting the Earth from
harmful gases and charged particles that
would destroy the atmosphere.

 Magnets are surrounded
by magnetic fields. A
magnetic field can be
thought of as consisting
of lines of force. The
forces of magnetic
attraction and repulsion
move along the lines of
force.

• All materials
exhibit some
degree of
magnetic
properties,
though some
are far more
magnetic than
others.
• The degree
of magnetism is
associated with
the degree of
mobility of a
substance's
electrons.
• Materials
such as iron,
in which the
electrons are
free to flow

 copper,
lead,
quartz,
water,
acetone, and
carbon
dioxide are
diamagnetic.
 very
weakly
affected by
magnetic
fields. To
the extent
that they
are
affected,
they become
magnetically

 sodium,
oxygen, iron
oxide (FeO or
Fe2O3), and
platinum
 affected
somewhat more
strongly than
diamagnetic
materials,
they become
polarized
parallel to a
magnetic
field. In a
nonuniform
magnetic
field, they
feel a force
towards the
higher field

 iron,
nickel,
gadolinium,
iron oxide
(Fe3O4),
Manganese
Bismuth
(MnBi), and
Cobalt Ferrite
(CoFe2O4).
 very strongly
affected by
magnetic
fields.
become
strongly
polarized in
the direction
of the
magnetic
field, thus,

1. Temporary: Some iron and iron alloys can be easily magnetized
by even a weak magnetic field. However, when the magnetic field
is removed, the object gradually loses its magnetism.
2. Permanent: Examples are alnico (Aluminum Nickel Cobalt alloy)
and ferrites (ceramic-like material that is made from a mix of iron
oxides with nickel, strontium, or cobalt). Once they are
magnetized, these objects do not easily lose their magnetism.
3. Electromagnets: These are used when a very strong magnet is
necessary. Electromagnets are made by placing a metal core
inside a coil of wire that is carrying an electrical current. The
electricity going through the wire produces a magnetic field. While
the electric current is flowing, the core acts as a strong magnet.
Computers, TVs, and electric motors use electromagnets.

 Ampere’s Circular
Current Theory of
Magnetism:
 Magnetism is
closely related to
electricity

 considers the molecular alignment
of the material.
 assumes that all magnetic
substances are composed of tiny
molecular magnets.
 any unmagnetized material has the
magnetic forces of its molecular
magnets neutralized by adjacent
molecular magnets, thereby
eliminating any magnetic effect.
 a magnetized material will have
most of its molecular magnets lined
up so that the north pole of each
molecule points in one direction, and
the south pole faces the opposite
direction.
 material with its molecules thus
aligned will then have one effective
north pole, and one effective south
pole.

 based on the electron spin
principle.
 an electron has a magnetic field
about it along with an electric field.
The effectiveness of the magnetic
field of an atom is determined by the
number of electrons spinning in
each direction.
 if an atom has equal numbers of
electrons spinning in opposite
directions, the magnetic fields
surrounding the electrons cancel
one another, and the atom is
unmagnetized.
 if more electrons spin in one
direction than another, the atom is
magnetized.

• https://micro.magnet.fs
u.edu/electromag/java
/magneticlines2/
• http://easyscienceforkid
s.com/all-about-earths-
magnetism/
• https://www.reference.co
m/science/magnetism-
10ef33adea83d9d3#
• http://webphysics.iupui
.edu/webscience/physics_
archive/magneticmateria