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2154 - Magnetism is a force that exerts attractive or
repulsive force on other materials. All
materials are influenced to a greater or lesser degree by the presence of a
magnetic field. All materials! Magnets come in two basic types, permanent magnets
and electromagnets. Magnetism is
ultimately the result of movement of an electric charge. The most common use of Nuclear Magnetic
Resonance is in medicine.
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---------------------------------- 2154 -
Extreme Magnetism
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- Magnetism is a force that exerts attractive
or repulsive force on other materials.
All materials are influenced to a greater or lesser degree by the
presence of a magnetic field. All
materials!
-
- Magnets come
in two basic types, permanent magnets and electromagnets. Magnetism is ultimately the result of
movement of an electric charge. If
electric charges flow through a conductor it is an electromagnetic. If an electron charge is spinning or orbiting
an atomic nucleus it is a permanent magnet
-
-. Permanent
magnets are created by spinning electrons inside a material such as iron. In most materials spinning electrons are
oriented in random, thus having no net magnetic affect. However, in some materials, those used to
produce permanent magnets, the spinning electrons can be oriented to all point
in the same direction. Thus a net
magnetic field can be produced in a north-south direction.
-
- In
electromagnets an electric current is run through a coil or loop of wire called
a solenoid. When an electric charge
moves it creates a magnetic field. By
moving it in circles you can create a net magnetic field and concentrate it in
a north-south direction.
-
- The N and S
directions or poles are arbitrary designations.
It is simply a way to identify opposite poles of a magnet’s attractive
or repulsive force. The north end of a
compass needle points north to the south magnetic pole of Earth .
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- By wrapping the coil of wire around a material
such as iron the strength of the magnetic field can be concentrated another 1000-fold.
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- The strengths
of a magnetic field are measured in Gauss and Tesla’s. 10,000 Gauss = 1 Tesla. The Tesla is a very large unit. Tesla is the magnetic force in newton per
ampere of current times meters of
distance. Tesla =
kilograms / amperes * seconds^2.
Tesla = magnetic flux / area. The
Tesla is so large it is easier to define the magnetic forces in milli-Tesla, or
1/1000th Tesla, or mT.
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--------------
10^-10 mT-------
the brain operates with magnet signals in this range.
--------------
0.05 -------------- the force of Earth’s magnetic field at
mid-latitudes. ------------------------------------- It is 0.03 at the equator and 0.06 at the poles
---------------
5 --------------- the magnetic field around the television
set..
--------------
10 ---------------- a refrigerator permanent magnet.
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300 --------------- the magnetic force of Solar Fares.
--------------- 1,500 -------------
the biggest permanent magnet
--------------
3,000 ------------
the magnetic field of an MRI in hospitals
--------------
45,000 ----------- the biggest electromagnet magnet, located at
Tennessee Tech.
--------------
800,000 --------- a short magnetic pulse created in a military
missile.
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- Sonoma State
University had a 17,000 mT cryogenically cooled electromagnet used in research. Electromagnets or solenoids come in two
types, resistive type electrical coils or superconductor coils that are super
cooled using liquid nitrogen or liquid helium (cryogenics).
-
- We have been
talking about stationary magnetic fields.
A pulsed magnetic field is a rapidly changing field. And, a moving magnetic field has other
properties. If a magnetic field is
moving it will generate an electric field.
A moving electric field in turn will generate a magnetic field.
-
- Alternating or oscillating electric / magnetic
fields are radiation. Electromagnetic radiation can have far
different effects on the environment and on biology than magnetism alone.
-
- Pulse magnets can generate short bursts of a
magnetic fields up to 100,000 mT for 0.25 milliseconds. These are mostly military applications and
there is a missile that can generate 800,000 mT for a microsecond that is a
bomb used to destroy all electronics over a wide area.
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- Stationary
magnetic fields up to 8,000 mT are considered to have no ill effects on
humans. A stationary electric field is
electrostatic. If you are not grounded
and you touch an electric capacitor containing an electric charge it can make
your hair stand up. Stationary electric
and magnetic fields up to these levels appear not to be harmful to
biology.
-
- The whole
story changes when either field is moving.
A moving magnetic field generates a current of electric charges in any
conductor. A moving electric charge
generates a magnetic field. And, vice a
versa, etc. when the two fields start oscillating back and forth the fields propagate
as electromagnetic radiation. We know
that many forms of electromagnetic radiation are harmful to biology. Microwave ovens, X-rays, Gamma Rays.
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- Our professor
was working around a magnet in Tennessee Tech. that had a strength of 32,000
mT. He felt no ill effects at the time,
but decided to try a little experiment.
He jerked his head to the side to look in the other direction. He immediately experienced vertigo and almost
passed out. A stationary magnet field
was no problem but a moving magnetic
field definitely had its affect. “ Don’t
do that”, was the lesson learned.
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- When a frog
was placed in a magnetic field up to 16,000 mT the diamagnetism (note 1) in its
body caused the frog to levitate inside the magnetic field. The frog appeared weightless and floated
around inside the magnetic cylinder like an astronaut in outer space.
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- Afterwards
the frog appeared fine and seemed to suffer no ill effects. However, a similar experiment was tried with
mice up to 32,000 mT and afterwards the mouse would run in circles
counter-clockwise. They decided to put
the mouse in the cylinder in the opposite directions and afterwards the mouse
began running in tight clockwise circles.
-
- The extreme
magnetism appeared to have some behavior effects. There is much more to be learned about extreme magnetism and its effects on
biology. All atoms are magnetic at some
level.
-
- The nucleus
of all atoms is composed of protons (positive charges) and neutrons. The nucleus is in constant movement. Charges in movement carry angular momentum
and create small magnetic fields. Physicists
call this angular momentum, spin.
-
- If there is an even number of protons and
neutrons in the nucleus they can pair up and the nucleus will have a net zero
spin. If the number of protons and
neutrons is odd than an intrinsic spin exists.
An element such as hydrogen 1 has a nucleus that is one proton. It has a spin of one.
-
- The angular momentum associated with intrinsic
nuclear spin can only occur at specific quantum levels. If the nuclei are placed in an alternating
magnetic field and the frequency of oscillation is tuned to the resonance of
the angular spin or precession of the nuclei a resonance can occur. The
precessing resonant spin of the nuclei can be in resonance with the oscillating
frequency of the electromagnetic field.
-
- Hydrogen
nuclei resonant in the Earth’s magnetic field, 0.05 mT, at 2,000 hertz. However, hydrogen nuclei in a 22,000 mT
magnetic field resonant at 900,000,000 hertz.
-
The most common use of Nuclear Magnetic Resonance is
in medicine, in Magnetic Resonance Imaging, MRI’s. The varying composition of Carbon 13 and
Hydrogen 1 nuclei in your body responds differently to different resonance
frequencies. Adding these responses all
up in slices and plotting all the directions allows computers to recreate a 3D
image of what is inside the body. It
takes a very powerful magnet , 3,000 mT.
These magnets are usually water cooled and contain no cryogenics, for
safety reasons.
-
- The MRI
starts with a strong static magnetic field to align the hydrogen or carbon 13
nuclei in the body. They then inject a
pulse of electromagnetic energy, a square wave pulse that contains many
harmonic frequencies. Certain
frequencies resonate with the nuclear precession and this resonance magnifies
the magnetic fields.
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- The combined
effects depends on the hydrogen, carbon medium be it tissue, bone, fat, blood,
etc. The measurements are spatially
encoded in slices and computer software recreates a 2D or 3D image. An entire chest cavity can be imaged in 30
seconds with no ill effects for the patient.
Resolution is possible down to a millionth of a cubic meter.
-
- Research laboratories can achieve even higher
resolution with more powerful magnets.
Computer Tomographic Scanning, or CT, does the same thing but uses
X-rays to acquire even higher resolution images. Magnetic fields are preferred in hospitals
because they can be made harmless to humans.
-
- Electron spin
and nuclear spin resonance for each element , or molecule, has a unique
spectrum of magnetic radiation absorption to create the resonance. This same
technique, as used in MRI’s, can be used in chemistry as spectroscopy.
-
- Research in
University produces crystals, or molecules, with magnetic properties that can
be studied up to 17,000 mT magnetic fields.
It is possible to map the surface and the structures of these
molecules. The molecules are normally
neutral but they can be modified to create an imbalance or net magnetic moment
for this type research.
-
- The MRI
technique is used in testing oil products and the production of timber products
(hydrocarbons). Learning breakthroughs
are occurring rapidly now that more powerful magnets are becoming commercially
available.
-
- We are
finding new ways of using them even though magnetism itself is still a
mystery. See Review 821 on Electric Charges. Magnetism is created by the movement of an
electric charge, but what is an Electric Charge?
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- (1) Diamagnetism occurs in materials whose atoms
have not permanent magnetic dipole moments, either orbital or intrinsic
nuclear. If an external magnetic field
is applied electrons switch their direction of orbit and a net opposing
magnetic field is produced. Diamagnetism
is present in all materials.
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- (2) Electric and magnetic fields are velocity dependent. Using the Theory of Relativity the two become
linked as an electromagnetic field and the electric field to one observer will
appear as a magnetic field to a second observer when there is relative
motion. So, electric fields and
magnetism become electromagnetism, and, space and time become space-time under
Einstein’s formulas.
(3) There are
all kinds of magnets everywhere: ATM and
credit cards, video and audio tapes, computer floppies and hard disks, CRT’s
and TV’s, speakers and microphones, transformers and telephones, refrigerator
decorations, motors and generators, atoms and stars, galaxies and black holes.
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- November 6, 2018. 820
-
August 27,2007. Professor Jeremy
Qualls, new to the faculty at SSU this year, gave a presentation on Extreme
Magnets.
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--- Some reviews are at: -------------- http://jdetrick.blogspot.com -----
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------ “Jim Detrick” -----------
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--------------------- Tuesday, November 06, 2018 -------------------------
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