Tuesday, November 6, 2018

Extreme Magnetism



-  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!
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-  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
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-.  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.
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-  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.
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-   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.
--------------  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).
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-  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.
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- Alternating or oscillating electric / magnetic fields are  radiation.   Electromagnetic radiation can have far different effects on the environment and on biology than magnetism alone.
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-    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. 
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-  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. 
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-  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.
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-  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.
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-    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.
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-   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.
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-   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.
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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.
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-  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.
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-    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.
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-  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.
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-   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.
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-  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. 
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-  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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 ---------------------   Tuesday, November 06, 2018         -------------------------
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