Rev. 13-Aug-04 GB
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The ancient Greeks knew that the mineral magnetite , named for the Magnesia region of Asia Minor, attracts small iron objects like nails. Magnetite is also known as lodestone .
Ancient Chinese discovered the compass in the year 271 AD (or CE).
The Chinese compass seen at the left uses a piece of magnetite shaped like a spoon.
The handle of the spoon points south.
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Peter Peregrinus (Pierre de Maricourt) was a member of the army of the King of Sicily and probably served as an engineer. In 1269 he described everything known about lodestones and how to make instruments using these magnets. He discovered the existence of magnetic poles and was the first to use the word "poles." (Latin polus .) He did experiments referring to how the north and south poles attract or repel.
He also described how to make a perpetual motion machine using magnets. People are still trying this (unsuccessfully) today!
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Gilbert published De Magnete (On the Magnet) in 1600. This book became a standard reference on electricity and magnetism in Europe. Gilbert was the first to distinguish the electric force
(named for the Greek word for amber) from the magnetic force. Gilbert debunked many folk myths about the curative properties of magnets.
William Gilbert, 1544-1603
Based on his observations of the preferred directions of thin iron needles near spherical lodestones, and the similarity of this phenomenon to the tendency of compass needles to tilt with respect to the horizontal plane as well as point north-south,
Gilbert deduced that the earth itself must be a giant magnet.
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“This premium quality magnetic bracelet will help relieve even the most severe or chronic discomfort in the hand, wrist, arm, elbow or shoulder. Constructed of surgical stainless steel with 24K titanium gold plating.”

Magnetic Material: Samarium Cobalt

Manufacturer's Rating: 11,000 Gauss

Surface Gauss: 1000 Gauss (each magnet)

Penetration:Polarity: North Pole (-) Brand: Serenity2000
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S
S
N
N attract
S repel
N
N
S
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S
S
S
S
S
S
N
N
N
N
N
N
The permanent magnet causes tiny magnetic domains in the nearby material to line up.
S N attract

This effect is most noticeable in ferromagnetic metals: iron, cobalt, nickel (& some “rare earth” elements).

In paramagnetic materials (like liquid oxygen), the magnetic domains line up weakly.

In diamagnetic materials (like silver), the domains line up against the permanent magnet and cause a weak repulsion.
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S
S saw cut
N
N S N
Scientists have searched in
 iron ore
 moon rocks
 cosmic rays
 high-energy colliders
 and many other places but “magnetic monopoles” have never been found.
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From N to S .
In direction of compass needle.
Try this web site: http://www.walter-fendt.de/ph11e/mfbar.htm
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Hans Christian Oersted
1777-1851
Oersted discovered in 1820 that electric current creates a magnetic field like a permanent magnet.
This is a Physics 2 topic, but we will use this effect in the Physics 1 activities involving magnetism.
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Inventions: a telephone repeater, rotating magnetic field principle, polyphase alternating-current system, induction motor, alternating-current power transmission, Tesla coil transformer, wireless communication, radio, fluorescent lights, and more than 700 other patents.
Nikola Tesla
1856-1943
The SI unit of magnetic field (actually magnetic flux density, but we don’t make a distinction in Physics 1) is the tesla, T.
The magnetic field in the gap between the rotor and stator of an electric motor is about 1 T.
We also sometimes use gauss. 1 T = 10,000 gauss.
The magnetic field in a typical home environment is about 0.1-1.0 gauss.
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1.
The magnetic force was known in ancient times.
2.
Magnets have two poles, N and S.
3.
Opposite poles attract, like poles repel.
4.
N and S poles are always in pairs, never alone.
5.
Electric currents also cause magnetic fields.
6.
Magnetic field lines start at N and go to S, following the direction of a compass needle.
7.
Units of tesla (T) and gauss. 1 T = 10,000 gauss.
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___ 1.
A scientist claims that he has discovered magnetic monopoles, and he sends you a sample cube of material that he claims contains only north magnetic poles. Which test below would help you verify or dispute his claim?
A) Check if all sides of the cube stick to a refrigerator door.
B) Measure the magnetic flux density (magnitude) near the surface to check if it exceeds the strongest normal magnet.
C) Hang the cube on a string and see if it is attracted to or repelled by a sphere with a negative electrical charge.
D) See if the south pole of a compass needle points toward all sides of the cube when placed near the respective sides.
E) No test would help you unless you had other samples of pure north and south poles to check for attraction and repulsion.
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___ 2.
If magnetic monopoles have never been discovered, what is/are the source(s) of magnetic fields?
A) Some elementary particles, like electrons, are tiny magnetic dipoles.
B) Moving electric charges create magnetic fields.
C) Since magnetic fields exist, there must be magnetic monopoles. We just haven’t discovered them yet.
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Objective of the Activity:
1.
Think about magnetic fields.
2.
Investigate the magnetic field created by a bar magnet.
3.
Learn how to measure magnetic fields using a Hall probe .
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