Download The Force and Nature of Magnetism

The Force and Nature of Magnetism
What Impact Does Magnetism Have In Our World?
Most people understand a magnet to be the
item you put on your refrigerator. What
the majority of the public does not know is
that without magnets, society would not
function like it does today.
The movement of charged particles causes
magnetism. To understand the magnetic
properties of a substance, one would need to
look at the motion of electrons within the
material. (Wysession, 2005)
Magnetic Resonance Image
www.hearthealthywomen.org
www.ak05.co.nz
Without the force of magnetism, or the knowledge of it, we
would not be able to navigate without the sun or stars. In
addition, we would not be able to run most electronics, from a
loudspeaker to a car or a plane. The medical field would not
be advanced enough to diagnose diseases within hours, or to
even detect cancerous tumors. Without magnetism, stores and
libraries would not be able to have anti-theft security systems.
Similarly, security forces such as those in airports would not
be able to scan people for weapons with metal detectors.
Migrating animals use magnetism to find their proper habitats
and without it entire species could die. In fact, without the
Earth’s magnetic field, the entire planet would erode away.
Magnetism is clearly an unseen force that our world depends
on immensely.
ELECTRONIC EVIDENCE #2
1
The Force and Nature of Magnetism
2
THE DISCOVERY OF MAGNETISM
Lodestone
www.clipart.dk.co.uk
Ancient societies of China, Rome, and Greece first
discovered magnetic forces. They observed that a
rock called the lodestone would attract other
lodestones. It has been discovered since that this
occurs because the lodestone contains iron ore, or
magnetite, which is a magnetic substance. Even
today, scientists have still not discovered what
makes lodestones magnetic, partly because it can be
found all around the world, not just in one particular
area. Some postulate that when lightning strikes a
rock rich in iron, a lodestone is formed.
(Coffey, 2011)
(Magnets & Magnetism, 2006)
The lodestone is a special type of the
mineral magnetite. All magnetite rocks
possess magnetism, but the lodestone
has a specific north south polarity.
Once early civilizations discovered
this, they began making the first
compasses.
(Brand, 2012)
The lodestone was used by many seafaring nations to
aid sailors in navigation. They would place a small
lodestone on a piece of wood and float the wood in
water. The sailors knew this would always point the
same direction, which we know today to be North.
This contraption was very handy when navigating
when the sun or stars were not visible, as that was the
usual method of navigation. The first known writings
on the utility of the lodestone as a compass can be
dated to 1269, when a Frenchman named Petrus
Peregrinus published some scientific writings.
(Magnets & Magnetism, 2006)
(Gunderson, 2005)
Lodestone
www.magnet.fsu.edu
The first known reference to the
lodestone and its abilities was by a
Greek philosopher, Thales of
Miletus, in 600 BC. Thales noted
its properties, but could only think
to attribute them to animism, a
phenomenon that suggests the
lodestone had a soul.
(Brand, 2012)
The Force and Nature of Magnetism
3
THE FIRST COMPASSES
1000 BC- Olmec’s located near San
Lorenzo, Veracruz, Mexico seemed to use
a bar of magnetized iron, which was a
part of a larger instrument, in orienting
their cities and buildings in a north-south
direction. Though this bar now points
approximately 35 degrees from magnetic
north, experts say it could have been
more reliable in the time it was used.
(Olmecs, 1975)
200 AD- Chinese civilizations sculpted
magnetite into spoon shaped compasses.
They called these early compasses south
pointers. Though they did not have all the
information we do at present, this name
acknowledges that compasses actually
point to the magnetic north pole, which is
in fact towards the geographic south of
the Earth. (Wysession, 2005)
1150- Chinese navigators began using
compasses with magnetic iron needles.
(Wysession, 2005)
1400’s- News of the Chinese magnetic
compass traveled to Europe and made
Columbus’s voyage to America in 1492
possible. (Pumfrey, 2000)
Chinese Compass
www.magnet.fsu.edu
Viking Compass
www.archaeology.org
Floating Compass
www.tcd.ie/
1500’s- A crystal called an Iceland spar was used
even on cloudy days to gather the sun’s position
within a few degrees of accuracy. This
transparent calcite crystal explains how Vikings
navigated. When light is passed through the
crystal, it is split in two, and by manipulating
these beams, Vikings looked for the point where
the beams were equally bright and lined up. This
place could show them the location of the sun.
(Swaminathan, 2012)
1700’s- Sir Augustus Charles Gregory, an
Australian Surveyor-General designed the
Gregory Pattern Compass that granted explorers
the ability to point to true north even through the
rough terrain. (Long Lost Compass, 2010)
The Force and Nature of Magnetism
1492- As Columbus was crossing the Atlantic, he
noticed the compass needle direction deviated slightly
from the north that the stars pointed to. As he
progressively got closer to the Americas, he noticed
the difference kept increasing. (Gunderson, 2005)
1400’s- Portuguese explorers who traveled long
distances in the Atlantic Ocean noticed that the small
errors that were insignificant for trips in the
Mediterranean Sea became more significant and
caused navigational errors. Then, they began
observing and recording the differences between the
compass and the sun to map these discrepancies.
(Leitao, 2011)
1500’s- Some of the observations of variations by
Portuguese sailors were attributed to failure of the
lodestone used to magnetize the compass needle or
the needle itself. (Keller, 2000)
1804- As Meriweather Lewis and William Clark
traversed the Louisiana Territory at U.S. President
Thomas Jefferson’s request, they recorded both
compass position and the placement of the sun or
North Star, as they knew relying on the compass
alone would be negligent because of its known
unreliability. (Ramsayer, 2003)
1818– Reverend George Fisher noticed that
magnetism disrupted the reading of a chronometer,
which determined time, and therefore longitude, when
at sea. (Roberts, 2009)
Declination
www.magnetic-declination.com
4
Map of Declination
www.thecompassstore.com
ion
D
Decelicnliatnation
All of these explorers discovered or
observed magnetic declination. Declination
is the phenomenon that proves the magnetic
poles are not in the same position as the
geographic poles. The geographic poles are
aligned with the Earth’s axis, whereas the
magnetic poles’ locations can vary.
Currently, the magnetic North Pole is in
northern Canada positioned at 81 degrees
north latitude, whereas the geographic
North Pole is located at 90 degrees north
latitude. Many scientists believe this
variation is caused by the nature of the
magnetic field of the Earth, also known as
the magnetosphere. When electric currents
pass through the Earth’s core, which is
made of molten iron, the magnetosphere is
created and altered. Because the currents
and the iron in the Earth’s core are flexible,
the magnetic poles move also. Since the
discovery of the magnetic north pole in
1831, it has moved about 800 kilometers. It
continues to drift at about 35 miles per year.
When a compass needle is shown to defer
from another indicator of north, magnetic
declination is showing. This happens
especially when one is close to the any of
the poles.
(Coffey, 2011)
(Gunderson, 2005)
(Wysession, 2005)
The Force and Nature of Magnetism
5
The Solution to
Magnetic Declination
The Dip Compass
The Earth’s Magnetic Field
www.physics.sjsu.edu/
Though we refer to the pole that the north
compass needle points to as the magnetic North
Pole, since the poles of a magnet, such as a
compass needle, are attracted to their opposite,
the compass is actually pointing to the magnetic
south pole. However, it is still normally called
magnetic north because geographically it is
located in the northern hemisphere. In addition,
the poles can switch when the magnetosphere
reverses. In fact, in the last 3.5 million years, the
poles have switched nine times.
(Wysession, 2005)
(Gunderson, 2005)
Modern Dip Needle
www.pasco.com
Early Dip Compass
www.etc.usf.edu
Many navigators had noticed that occasionally
compasses would point downward instead of just
horizontal direction. In 1581, Robert Norman, an
untrained compass maker, observed this
phenomenon while flying over the poles. Norman
then tried to make the compass vertical to see how
the needle would react. This apparatus was a dip
needle. A dip needle is similar to a compass in the
make, but is used primarily close to the poles.
Because compasses become unreliable near the
poles, navigators now use dip needles to show the
inclination of the Earth’s magnetic field, and
therefore the location of north when they near the
poles.
(Gunderson, 2005)
(Pumfrey, 2000)
The Force and Nature of Magnetism
6
Bar Magnets
www.cpsc.gov
Horseshoe Magnet
www.magnetmaterialyl.com
Domain Diagram
www.magnet.fsu.edu
Magnets like these are made of
different cells, called domains. All of
the molecular magnets in one domain
point in one direction, which makes it
a small magnet. However, because all
the neighboring domains point in
different directions the entire material
is not a magnet. When all the
domains are pointing in different
directions, their magnetization
cancels out. Once magnetized, all the
domains line up to point in the same
direction. Then the magnetic forces
of each domain reinforce each other.
This is known as the domain theory
of magnetism.
(Magnets & Magnetism, 2006)
(Gunderson, 2005)
Magnetic Poles
All magnets have 2 poles, a
north pole and a south pole.
Even if a magnet is cut in half,
it will still form two poles.
Similar poles repel each other.
Therefore, a north pole will
never be attracted to another
north pole. Unlike poles
attract, so one will always see
north and south poles pulled
together.
(Magnets & Magnetism, 2006)
(Gunderson, 2005)
(Kirkland, 2007)
Magnetic Force
www.education.vic.gov.au
Magnetic Force
A magnet can exert force
on other magnets or magnetic
objects. This force can cause
another object to move or
change. The force of a magnet is
strongest nearest its poles.
Magnetic force can even act
over a distance, though the force
will diminish with distance.
(Wysession, 2005)
(Kirkland, 2007)
Pole Attraction
www.howmagnetswork.com
TERIALS
MAGNETIC MA
Not every metal is attracted to a magnet.
Only iron, steel, nickel, cobalt, and other
magnets can be affected by a magnet’s
magnetic force.
(Magnets & Magnetism, 2006)
The Force and Nature of Magnetism
Magnetic Fields
Magnetic Field of a Bar Magnet
www.ece.neu.edu
7
Around every magnet there is an invisible field where the
force of the magnet can be detected. This space is the
magnetic field of a magnet. The field is usually stronger
near the poles and the further you get away from the
magnet, the weaker the field gets. Lines can display the
magnetic field of a magnet. These field lines begin at the
north pole and extend around the magnet to the south
pole. The closer the lines are together, the stronger the
magnetic force at that point. To find the magnetic field of
a magnet you place a piece of paper over the magnet and
sprinkle iron filings over it and the field lines will form
out of the filings.
(Magnets & Magnetism, 2006)
(Wysession, 2005)
CREATION OF A MAGNET
While there are naturally magnetic
rocks found on Earth, most magnets
used today are manmade. There are two
different ways to create a magnet.
(Magnets & Magnetism, 2006)
www.mgitecetech.wordpress.com
ELECTRIC METHOD
This creates an
electromagnet, which
utilizes electricity to
create a magnetic field.
(Wysession, 2005)
Place a steel or
iron bar, such as a
nail, inside a
solenoid, or coil of
wire, then attach
both ends of the
wire to either end
of a battery. Pass
current
through
the solenoid using
the battery and a
magnetic
field
forms around the
nail.
(Wysession, 2005)
Single Touch Method
www.need.org
M IC R O S O FT
Single Touch Method
Stroke one pole of a bar magnet
in the same direction on a
magnetic object, such as a
needle, 10 to 15 times.
(Magnets & Magnetism, 2006)
The Force and Nature of Magnetism
8
MI CRO S O FT
Hard & Soft Magnetic Materials
Diamagnetic– materials
align in opposition to an
applied magnetic field.
Ferromagnetic– materials
become magnetic in the
presence of another
magnetic field and remain
magnetic after the external
field is removed.
Paramagnetic– materials
become strongly magnetic
in the presence of an
external magnetic field,
but return to their original
state when the force is
removed. This
phenomenon is induced
magnetism.
(Magnets & Magnetism,
2006)
(Wysession, 2005)
Iron and similar materials are easily magnetized. This
means the domains in the material line up in the same
direction easily. However, once the magnetic influence
is removed, the substance loses its magnetism because
the domains revert to pointing in different directions.
These are soft materials that serve as excellent
temporary magnets. These soft materials are used in
electromagnets, so the material loses its magnetism
once the current is turned off. Steel on the other hand is
a hard, or ferromagnetic, material. This means it is
difficult to line up the domains in the same direction,
and therefore difficult to magnetize. However, once the
domains do line up, they remain in that position after
the magnetic influence is removed, creating a
permanent magnet. However, even with a magnet made
out of a hard material, if it is jolted or dropped, it can
lose its magnetism eventually.
(Magnets & Magnetism, 2006)
Electromagnets
www.how-things-work
-science-projects.com
H PU
In an electromagnet, the uniform motion
of electrons throughout the solenoid
creates the magnetic field. Therefore,
when the power source, normally a
battery, is connected, the current is
flowing through the solenoid and the
ferromagnetic material inside it
emanates a magnetic field. However,
when the power source is not releasing
current, there is no magnetic field.
(Wysession, 2005)
The strength of an electromagnet depends on
the amount of current, number of loops in the
solenoid, and its type of ferromagnetic core.
(Wysession, 2005)
Powerful Electromagnet
www.howstuffworks.com
Electromagnetism was first found in 1820 when
Danish scientist Hans Christian Oersted
observed that as electric current passed through
a wire, a nearby compass needle twitched. After
years of study, in 1845 Michael Faraday
developed the theory of electromagnetism as
we use it today.
(Highfield, 2010)
The Force and Nature of Magnetism
9
REAL WORLD APPLICATIONS
BIOMAGNETS
Transportation
Magnetism is powerful enough to levitate a
train. Magnetically levitated trains, or
MAGLEV trains, use electromagnets to lift
the train cars off the ground. Then, these
trains travel along thin magnetic tracks,
which can propel the trains up to 300 miles
per hour. This speed is not possible with
normal train tracks as friction slows the
train significantly. So far, only Japan and
Germany have perfected and implemented
MAGLEV trains.
(McCartney, 2008)
(Gunderson, 2005)
Companies that create
biomagnets claim they increase
healing and decrease pain by
affecting charged particles in the
bloodstream to flow faster and
therefore increase circulation.
Biomagnets are not approved by
the FDA however, so their usage
has not become widespread yet.
(Gunderson, 2005)
MAGLEV Train
www.railsystem.net
Information
Storage
Information can be
stored on a small
magnetic strip on a
card. These cards
can be used for
credit cards, debit
cards, laundry
machines, parking
meters, and copiers.
Tape recorders and
computer disks also
store information in
magnetic fields.
(Kirkland, 2007)
Gas Gauge
www.wemausa.com
Galvanometers
A galvanometer uses an
electromagnet to move
a pointer on a dial. The
pointer measures the
amount of current in the
solenoid. This type of
device is used in cars to
measure the amount of
gas remaining in the
tank. A sensor in the
tank reduces the current
as the level decreases
and the pointer reacts.
(Wysession, 2005)
Electromagnets
Credit Card Magnetic Strip
www.teach-ict.com
Traffic Light
www.drcarolshow.com
Many common items use electromagnets, such as
electric motors, loudspeakers, electric bells, relay
switches, microphones, televisions, metal detectors,
traffic light sensors, and computers.
(Wysession, 2005)
(Gunderson, 2005)
The Force and Nature of Magnetism
10
REAL WORLD APPLICATIONS
Anti-Theft Devices
www.medwow.com
MRI MACHINES
Magnetic resonance imaging machines were
invented by Sir Peter Mansfield in the 1970’s as a
way to obtain two-dimensional images of the
human body. An MRI machine uses a very
powerful manmade magnetic field 40,000 times
stronger than the Earth's to look at the tissues and
organs in the human body. An MRI machine uses
four different magnets. The first magnet is very
powerful and is used to immerse the patient in a
large steady magnetic field. The other three
magnets create variable fields each in a different
dimension. One set goes head to toe along the
length of the body. The next magnet goes from the
top of the body through it to the bottom. The final
magnet goes left to right through the body width
wise. This method is much more effective then xrays, which are more appropriate for examining
bones. In addition, x-rays are more dangerous
because prolonged exposure to that type of
radiation can be harmful to the body. Therefore,
the advent of magnetic resonance imaging changed
the medical field immensely as now infections can
be safely diagnosed in hours instead of days.
(Rezende, 2006) (Wysession, 2005)
(Kirkland, 2007) (Hamzelou, 2011)
In the 1960’s a security device was invented using
electromagnetic waves to identify objects that have
been tagged with magnetic material. An activated
tag is demagnetized, so when it passes through the
electromagnetic current passing in between the
pedestals normally located in front of the exit doors,
the waves being to magnetize the tag. A receiver in
the pedestals detects the change in the domains of
the tag and sets off the alarm sound. A deactivated
tag has been magnetized after being checked out by
powerful magnets often housed in a rubber pad.
Then, since the tag is already magnetized, its
domains do not change as it goes through the
electromagnetic waves, and therefore does not set
off the alarm.
(Wysession, 2005)
Anti-Theft Pedestals
www.ambaelectronics.com
Metal detectors also use magnetic fields
produced by electric current to detect any
ferromagnetic material such as iron and steel that
is in most weapons like guns and knifes. If the
sensitivity of a metal detector is high, it will also
set off the alarm when it senses other metal
objects, such as coins. (Metal Detector, 2005)
The Force and Nature of Magnetism
Magnetoreception
Intense research and numerous studies
have shown that many animals
including robins, bacterium, warblers,
lobsters, salmon, zebrafish, trout,
sharks, rays, loggerhead turtles, naked
mole rats, bats, pigeons, cattle, monarch
butterflies, honeybees, ants, elephant
seals, and whales all have a special
sense called magnetoreception. This
sense allows them to have the ability of
a compass, that is, to know
directionality and navigate through
unknown areas. Some of these animals
have even shown the ability to not only
sense direction, but also distance from
the poles.
(Yong, 2010) (Castelvecchi, 2012)
11
Magnetic storms are disruptions in the Earth’s
magnetic field. These changes can be sensed on
the ground using magnetometers. Magnetometers
measure the magnitude of magnetic storms in units
of Teslas with comparison to time. These records
can then be plotted to show the progression of a
storm. The Pythagorean Theorem can also be used
to calculate the magnitude of a magnetic field.
However, because magnetism exists in three
dimensions, this requires the three dimensional
Pythagorean Theorem, which is
D  x2  y 2  z 2
where x, y, and z are the coordinates of a point in
space. This formula can be used to calculate which
cities have the highest magnetic field strengths.
(Odenwald, 2006)
Magnetic Storm Graph
www.image.gsfc.nasa.gov
CONNECTIONS OF MAGNETISM
MATH AND SCIENCE
Loggerhead Sea Turtle
www.mydailyclarity.com
The Earth's magnetic field serves many
purposes, one of which is protection. The
magnetic field guards the earth from solar
wind that could eventually eradicate the
planet. In fact, Jupiter has begun to erode
due to solar wind, though its strong magnetic
field has allowed it to recapture escaping
gases and therefore maintain its mass.
(Semenivk, 2009) (Gaensler, 2009)
Earth’s Magnetic Field Deflecting Solar Wind
www.astronomygcse.co.uk
The Force and Nature of Magnetism
12
References
Brand, M., Neaves, S., & Smith, E. (2012). Lodestone. National High Magnetic Field Laboratory.
Retrieved from http://www.magnet.fsu.edu/education/tutorials/museum/lodestone.html.
Castelvecchi, D. (2012). The compass within. Scientific American, 306(1), 48.
Coffey, R. (2011). 20 things you didn’t know about magnetism. Discover, 32(6), 96.
Did Olmecs have first compass? (1975). Science News, 108(10), 148.
Gaensler, B. (2009). The magnetic universe. Australian Science, 30(1), 22-25.
Gunderson, P.E. (2005). Magnetism, electromagnetism, and electronics. Handy Physics Answer Book. Canton, MI:
Visible Ink Press.
Hamzelou, J. (2011). Magnets cut diagnosis time for infections by days. New Scientist, 210(2810), 9.
Highfield, R. (2010). Electromagnetism. New Scientist, 207(2777), 34.
Keller, A. (2000). Navigation. Encyclopedia of the Scientific Revolution, 453.
Kirkland, K. (2007). Electricity and Magnetism. New York, NY: Facts on File.
Leitao, H. & Alvaraz, W. (2011). The Portuguese and Spanish voyages of discovery and the early history of geology.
Geological Society of America Bulletin, 123(7), 1226-1228.
Magnets & magnetism. (2006). Research Machines, 1.
McCartney, R., Deroche, S., & Pontiff, D. (2008). Can trains really float? Science & Children, 45(7), 33.
Metal detector. (2005). Aviation Week & Space Technology, 163(8), 84.
Odenwald, S. (2006). Extra credit problems in space science. Exploring Space Science Mathematics, 14 & 17. Retrieved
from http://image.gsfc.nasa.gov/poetry.
Proof of long-lost compass. (2010). Australian Geographic, (99), 19.
Pumfrey, S. (2000). Compass, magnetic. Encyclopedia of the Scientific Revolution, 156.
Ramsayer, K. (2003). North vs. northwest. Science News, 164(14), 213.
Rezende, L. (2006). Chronology of Science. New York, NY: Facts on File.
Roberts, G.W. (2009). Magnetism and chronometers: The research of Reverend George Fisher. British Journal for the
History of Science, 42(1), 57-72.
Semenivk, I. (2009). Can magnetism save a vaporizing planet? Sky & Telescope, 118(6), 16.
Swaminathan, N. (2012). The Vikings’ Crystal Compass? Archaeology, 65(2), 20.
Wysession, M., Frank, D., & Yancopoulos, S. (2005). Physical Science Concepts in Action: Teacher’s Edition for North
Carolina. Upper Saddle River, NJ: Pearson Education.
Yong, E. (2010). Masters of magnetism. New Scientist, 208(2788), 2.
Pictures
www.ak05.co.nz
www.ambaelectronics.com
www.archaeology.org
www.astronomygcse.co.uk
www.clipart.dk.co.uk
www.cpsc.gov
www.drcarolshow.com
www.ece.neu.edu
www.education.vic.gov.au
www.etc.usf.edu
www.hearthealthywomen.org
www.howmagnetswork.com/
www.howstuffworks.com
www.how-things-work-science-projects.com
www.image.gsfc.nasa.gov
Pictures
www.magnet.fsu.edu
www.magnetic-declination.com
www.magnetmaterialyl.com
www.medwow.com
www.mgitecetech.wordpress.com
www.mydailyclarity.com
www.need.org
www.pasco.com
www.physics.sjsu.edu/
www.railsystem.net
www.tcd.ie/
www.teach-ict.com
www.thecompassstore.com
www.wemausa.com