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Magnetism
By Enkoosh Oyunbazar and Kinleigh O’Connor
What is Magnetism?
• Magnetism is the force of attraction or repulsion
of a magnetic material due to the arrangement
of its atoms, particularly its electrons.
• A magnet is an object that exhibits a strong
magnetic field and will attract materials, like iron,
to it.
• Magnets have two poles, called the north (N)
and south (S) poles. Two magnets will be
attracted by their opposite poles, and each will
repel the like pole of the other magnet.
History of Magnetism
• The Chinese and Greeks knew about the
magical properties of magnets. The ancient
Greeks used a stone substance called
“magnetite.” They discovered that the stone
always pointed in the same direction.
• Later, stones of magnetite called “lodestones”
were used in navigation.
• William Gilbert, an English physician, first
proposed in 1600 that the earth itself is a
magnet, and he predicted that the Earth would
be found to have magnetic poles.
• The term Magnetism comes from the
ancient Greek city of Magnesia, where many
natural magnets were found. We now refer
to these natural magnets as lodestones
which contain magnetite, a natural magnetic
material - Fe3O4.
• Pliny the Elder (23-79 AD Roman) wrote of
a hill near the river Indus that was made
entirely of a stone that attracted iron.
Magnetic Fields
• Magnetic Fields are:
– The region where magnetic force exists
around a magnet or any moving charged
object.
– Produced by electric currents, which can be
macroscopic (seen with human eye)
currents in wires, or microscopic (unable to
be seen with human eye) currents
associated with electrons in atomic orbits.
• Dipolar in nature. Meaning that they have a north and
south magnetic pole.
• If broken, you will end up with multiple smaller magnets.
The will not just have a north or south pole, they will have
both.
• The SI unit for magnetic field is the Tesla (flux density),
which can be seen from the magnetic part of the
Lorentz force law:
• A smaller magnetic field unit is the Gauss (1 Tesla =
10,000 Gauss).
Magnetic Flux Lines
• Magnetic Flux lines:
Are imaginary lines that map out the magnetic field
around a magnet.
Always form closed loops and never intersect.
The SI unit of magnetic flux is the weber (measures
the number of lines of flux), and the unit of
magnetic field is the weber per square meter, or
tesla.
• Concentrated lines of flux emerge from the north
pole of the magnet; curve around the magnet, and
then enter the south pole of the magnet.
• The direction of the magnetic field inside the magnet
is from the south to the north pole. Outside of the
magnet, the field lines will go from north to south.
Magnetic Field
Strength
• The number of magnetic lines of flux per unit
area, passing through a plane perpendicular to
the direction of the lines.
• Also known as the Flux Density.
• Magnetic Field Strength is a vector quantity.
QUIZ!!!
1. What is the force of attraction or repulsion of a
magnetic material due to the arrangement of its atoms?
______________.
2. Magnets have a north and south __________.
3. Who proposed that the Earth itself was a magnet?
______________.
4. What is the region where magnetic force exists around a
magnet or any moving charged object?
______________.
5. What is the SI unit for a magnetic field? ___________.
6. What are imaginary lines that map out the magnetic
field around a magnet? _______________.
7. Magnetic Field Strength is a ____________ quantity.
ANSWERS!!
1. What is the force of attraction or repulsion of a
magnetic material due to the arrangement of its
atoms? Magnetism.
2. Magnets have a north and south Pole.
3. Who proposed that the Earth itself was a magnet?
William Gilbert.
4. What is the region where magnetic force exists around
a magnet or any moving charged object? Magnetic
Field.
5. What is the SI unit for a magnetic field? Tesla.
6. What are imaginary lines that map out the magnetic
field around a magnet? Magnetic Flux Lines.
7. Magnetic Field Strength is a Vector quantity.
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http://www.school-for-champions.com/science/magnetism.htm
http://en.wikipedia.org/wiki/Magnetism
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magfie.html
http://hyperphysics.phy-astr.gsu.edu/Hbase/magnetic/magfield.html
http://hyperphysics.phy-astr.gsu.edu/Hbase/magnetic/fluxmg.html
Magnetism
By:
Megan O’Connor
&
Chrissy Moffatt
Background
• Magnetism was derived from Magnesia, the
name of a region in Asia Minor.
• Lodestone was found, that is a naturally
magnetic iron ore.
• Iron is not the only metal that is simply
magnetized when positioned in a magnetic
field.
Ex: Nickel and Cobalt
Basics of Magnetism
• Force of pull or repulsion that acts at a
distance.
• It is caused by moving electrically charged
particles in magnetic objects
example: Magnets
Magnets
• A material in which the spinning electrons of
its atoms are aligned with one another=
magnetic force.
• Has two ends called poles where the magnetic
force is the strongest.
~North Pole
~South Pole
Electromagnets
• Form magnets by using electricity
• Can be formed with a battery and copper wire
coiled around a metal rod such as a nail.
Repulsion
• Two magnetic objects that have like poles
facing each other, the magnetic force pushes
them apart.
Attraction
• Two magnets that are unlike and close to each
other, there is a force that attracts the poles
together.
Magnetic Fields
• Region where magnetic force exists around a
magnet or any moving charged object.
• Consists of imaginary lines of flux coming from
moving or rotating electrically charged
particles
• Magnetic lines do not cross
Magnetic field or lines of flux
of a moving charged particle
Magnetic Field Strength
• The number of magnetic flux lines per unit
area passing through a plane perpendicular to
the direction of the lines; vector quantity.
• The unit of magnetic flux is Weber
Questions:
1. Magnetism derived from:
a. Troad
b. Pontus
c. Magnesia
d. Mysia
2. The spinning electrons of its atoms are aligned with one another is
called
a. Magnetic Lines
b. Magnetic Fields
c. Electromagnetic Force
d. Magnetic Force
3. What are the two places that the magnetic forces are the
strongest?
a. poles
b. magnets
c. particles
Questions continued……..
4. What is the unit of magnetic flux
a .joule
b. weber
c. coulomb
d. ampere
5. Electromagnets are formed by using
a. electricity
b.h2o
c. fish oil
d. friction
6. A magnetic field is produced by
a. Stationary ions
c. Moving electrons
b. Stationary protons
d. Moving protons
Answers!!!!!!!!!!!!!!!!!
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1.
2.
3.
4.
5.
6.
C
D
A
B
A
C