Magnetic Levitation Power Point

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

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