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8/6/2019 Magnetic Levitation Power Point
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MAGNETIC
LEVITATION
B Y - A R C H I T E N 3 R D 0 8 0 0 3 2 1 4 0 3
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WHAT IS A MAGNET?
It is simply an object which produces amagnetic field
North and South are the designations madeto describe the two opposite poles
North is attracted to South and repelled byNorth
South is attracted to North and repelled bySouth
There are three main types:
- Permanent Magnets- Soft Magnets- Electromagnets
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PERMANENT MAGNETS
Electrons fill atomic orbitals in pairs
If an orbital is full, then one electron spinsupward and the other spins downward(Pauli Exclusion Principle), so theirmagnetic fields cancel out
If an orbital is not full, then the movementof the electron creates a tiny magneticfield
Atoms with several unpaired orbitals havean orbital magnetic moment
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PERMANENT MAGNETS
In metals, the orbital magnetic
moment causes nearby atoms
to align in the same direction,creating a ferromagnetic metal
The strength of the magnetic field
decreases inversely with the
cube of the distance from themagnets center
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SOFT MAGNETS
These types of magnets do not have a magnetic field of their own
However, when put in the presence of another objects magnetic field, they are
attracted (paramagnetic)
Once the external magnetic field is removed, they return to their nonmagnetic state
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ELECTROMAGNETS
The magnetic field is caused by the flowof an electric current
The simplest example is a coiled piece
of wire
Using the right hand rule, it is possibleto determine the direction
An advantage over permanent magnets
is that the magnetic field strengthcan be changed by changing thecurrent
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NINEWAYS TO MAGNETICALLY LEVITATE
AN OBJECT
Mechanical constraint
Direct diamagnetic levitation
Superconductors
Diamagnetically-stabilized levitation
Rotational stabilization
Servo stabilization
Rotating conductors beneath
magnetsHigh-frequency oscillating
electromagnetic fields
Translational Halbach arrays andInductrack
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DirectDiamagnetic Levitation HowitWorks
Diamagnetic materials repel a magneticfield
All materials have diamagnetic properties,
but the effect is very weak, and usuallyovercome by the objects paramagneticor ferromagnetic properties, which actin the opposite manner
By surrounding a diamagnetic materialwith a magnetic field, it can be held in astationary position (the magnetic forceis strong enough to counteract gravity)
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DirectDiamagnetic Levitation Applications
Water is primarily diamagnetic, so water droplets and
objects that contain large amounts of water can be
levitated
http://www.hfml.ru.nl/pics/Movies/frog.mpg
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SUPERCONDUCTORS
A superconductor is an element, inter-metallic alloy, or acompound that will conduct electricity without resistancebelow a certain temperature.
Resistance produces losses in energy flowing through thematerial.
In a closed loop, an electrical current will flow continuouslyin a superconducting material.
Superconductors are not in widespread use due to the cold
temperatures they must be kept atHighest Tc found 150K
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APPLICATIONS
MagLev Trains- The magnetized coil running alongthe track, repels the large magnets on the train'sundercarriage, allowing the train to levitate
Biomagnetism- in MRI and SQUID (measures
slight magnetic fields)Particle accelerators to accelerate sub-atomicparticles to nearly the speed of light
Electric generators- made with superconductingwire: They have a 99% efficiency and have abouthalf the size of conventional generators.
Really fast computers- In "petaflop" computers. Apetaflop is a thousand-trillion floating pointoperations per second. Today's fastest computingoperations have only reached "teraflop" speeds.
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Applicationssoontocome
Stabilizing momentum wheel (gyroscope) for earth-orbitingsatellites- can reduce friction to near zero
Superconducting x-ray detectors and superconducting lightdetectors - able to detect extremely weak amounts ofenergy.
Superconducting digital router- for high-speed data
communications up to 160 GhzPower plants use to reduce greenhouse gas emissions
Advancements depend to a great degree on advancements inthe field of cryogenic cooling or finding more high-temperature superconductors
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ROTATIONAL MAGNETISM
Also known as spin stabilized magnetic levitation
Happens when the forces acting on the levitating object- gravitational, magnetic, and
gyroscopic- are in equilibrium
Earnshaws theorem says it is impossible
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SUPER LEVITRON
Two opposing neodymium-iron-boron permanent magnets.
original invention by Roy Harrigan and patented in 1983.
He didnt known about Earnshaws theorem which many thoughtsaid such an invention was impossible.
The rotation of a spinning objects axis of spin creates a toriod ofgenuine stability in a way that does not violate Earnshaws
theorem, but that went completely unpredicted by physicists formore than a century.
The top remain levitating in a central point in space above the basewhere the forces acting on the top- gravitational, magnetic, andgyroscopic- are in equilibrium
Stops due to air resistance
http://www.levitron.com/images/levitron.mpghttp://www.levitron.com/images/levitron-drbob.mpg
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WHY ITWORKS
The principle is that two similar poles (e.g.,two north's) repel, and two different polesattract, with forces that are stronger whenthe poles are closer. There are fourmagnetic forces on the top: on its northpole, repulsion from the base's north andattraction from the base's south, and on itssouth pole, attraction from the base's northand repulsion from the base's south.Because of the way the forces depend ondistance, the north-north repulsiondominates, and the top is magneticallyrepelled. It hangs where this upwardrepulsion balances the downward force of
gravity, that is, at the point of equilibriumwhere the total force is zero.
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HOW TO GET IT TOWORK
Correct magnetic strengths
Mass of the top must be right
within .5%Magnets are temperaturedependent, weaker in warmertemperatures
Correct spinning rate (not toofast or slow)
Must be introduced onto a smallstabile region only millimeters
wide and high
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REFERENCES
http://www.physics.ucla.edu/marty/levitron/spinstab.pdf
http://www.superconductors.org/uses.htm
http://www.popsci.com/popsci/how20/be199aa138b84010vgnvcm1000004eecbccdrcrd.html
http://www.chem.yale.edu/~chem125/levitron/levitron.html
http://science.howstuffworks.com/magnet3.htm
http://www.howstuffworks.com/electromagnet.htm
http://en.wikipedia.org/wiki/Magnet
http://en.wikipedia.org/wiki/Electromagnet
http://en.wikipedia.org/wiki/Magnetic_levitation
http://my.execpc.com/~rhoadley/maglev.htm
http://www.hfml.science.ru.nl/hfml/froglev.html