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.

Like poles repel and

• 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

about in a sea

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

polarized in

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

region.

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,

they are

1. Temporary: Some iron and iron alloys can be easily magnetizedby even a weak magnetic field. However, when the magnetic fieldis 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 ironoxides with nickel, strontium, or cobalt). Once they aremagnetized, these objects do not easily lose their magnetism.

3. Electromagnets: These are used when a very strong magnet isnecessary. Electromagnets are made by placing a metal coreinside a coil of wire that is carrying an electrical current. Theelectricity going through the wire produces a magnetic field. Whilethe 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

ls.html