Magnetic Magnetic LevitationLevitation

Tori Johnson and Jenna WilsonTori Johnson and Jenna Wilson

What is a magnet?What is a magnet?

It is simply an object which produces a It is simply an object which produces a magnetic fieldmagnetic field

North and South are the designations North and South are the designations made to describe the two opposite polesmade to describe the two opposite poles

North is attracted to South and repelled North is attracted to South and repelled by Northby North

South is attracted to North and repelled South is attracted to North and repelled by Southby South

There are three main types:There are three main types:- Permanent Magnets- Permanent Magnets- Soft Magnets- Soft Magnets- Electromagnets- Electromagnets

Permanent MagnetsPermanent Magnets

Electrons fill atomic orbitals in pairsElectrons fill atomic orbitals in pairs If an orbital is full, then one electron If an orbital is full, then one electron

spins upward and the other spins spins upward and the other spins downward (Pauli Exclusion Principle), downward (Pauli Exclusion Principle), so their magnetic fields cancel outso their magnetic fields cancel out

If an orbital is not full, then the If an orbital is not full, then the movement of the electron creates a movement of the electron creates a tiny magnetic fieldtiny magnetic field

Atoms with several unpaired orbitals Atoms with several unpaired orbitals have an have an orbital magnetic momentorbital magnetic moment

Permanent MagnetsPermanent Magnets

In metals, the orbital magnetic In metals, the orbital magnetic moment causes nearby atoms moment causes nearby atoms to align in the same direction, to align in the same direction, creating a ferromagnetic creating a ferromagnetic metalmetal

The strength of the magnetic The strength of the magnetic field decreases inversely with field decreases inversely with the cube of the distance from the cube of the distance from the magnet’s centerthe magnet’s center

Soft MagnetsSoft Magnets

These types of magnets do not have a These types of magnets do not have a magnetic field of their ownmagnetic field of their own

However, when put in the presence of However, when put in the presence of another object’s magnetic field, they are another object’s magnetic field, they are attracted (paramagnetic)attracted (paramagnetic)

Once the external magnetic field is Once the external magnetic field is removed, they return to their removed, they return to their nonmagnetic statenonmagnetic state

ElectromagnetsElectromagnets

The magnetic field is caused by the The magnetic field is caused by the flow of an electric currentflow of an electric current

The simplest example is a coiled The simplest example is a coiled piece of wirepiece of wire

Using the right hand rule, it is Using the right hand rule, it is possible to determine the direction possible to determine the direction

An advantage over permanent An advantage over permanent magnets is that the magnetic field magnets is that the magnetic field strength can be changed by strength can be changed by changing the currentchanging the current

Nine Ways to Nine Ways to Magnetically Levitate an Magnetically Levitate an ObjectObject

Mechanical constraintMechanical constraint Direct diamagnetic levitationDirect diamagnetic levitation SuperconductorsSuperconductors Diamagnetically-stabilized Diamagnetically-stabilized

levitationlevitation Rotational stabilizationRotational stabilization Servo stabilizationServo stabilization Rotating conductors beneath Rotating conductors beneath

magnetsmagnets High-frequency oscillating High-frequency oscillating

electromagnetic fieldselectromagnetic fields Translational Halbach arrays Translational Halbach arrays

and Inductrack and Inductrack

Direct Diamagnetic Direct Diamagnetic Levitation – How it WorksLevitation – How it Works Diamagnetic materials repel a Diamagnetic materials repel a

magnetic field magnetic field All materials have diamagnetic All materials have diamagnetic

properties, but the effect is very properties, but the effect is very weak, and usually overcome by the weak, and usually overcome by the object‘s paramagnetic or object‘s paramagnetic or ferromagnetic properties, which act in ferromagnetic properties, which act in the opposite mannerthe opposite manner

By surrounding a diamagnetic By surrounding a diamagnetic material with a magnetic field, it can material with a magnetic field, it can be held in a stationary position (the be held in a stationary position (the magnetic force is strong enough to magnetic force is strong enough to counteract gravity)counteract gravity)

Direct Diamagnetic Direct Diamagnetic Levitation – ApplicationsLevitation – Applications

Water is primarily Water is primarily diamagnetic, so water diamagnetic, so water droplets and objects that droplets and objects that contain large amounts contain large amounts of water can be levitatedof water can be levitated

http://www.hfml.ru.nl/http://www.hfml.ru.nl/pics/Movies/frog.mpg pics/Movies/frog.mpg

SuperconductorsSuperconductors A superconductor is an element, inter-metallic alloy, A superconductor is an element, inter-metallic alloy,

or a compound that will conduct electricity without or a compound that will conduct electricity without resistance below a certain temperature.resistance below a certain temperature.

Resistance produces losses in energy flowing through Resistance produces losses in energy flowing through the material.the material.

In a closed loop, an electrical current will flow In a closed loop, an electrical current will flow continuously in a superconducting material. continuously in a superconducting material.

Superconductors are not in widespread use due to the Superconductors are not in widespread use due to the cold temperatures they must be kept at cold temperatures they must be kept at

Highest Tc found 150K Highest Tc found 150K

ApplicationsApplications

MagLev Trains- The magnetized coil MagLev Trains- The magnetized coil running along the track, repels the large running along the track, repels the large magnets on the train's undercarriage, magnets on the train's undercarriage, allowing the train to levitateallowing the train to levitate

Biomagnetism- in MRI and SQUID Biomagnetism- in MRI and SQUID (measures slight magnetic fields)(measures slight magnetic fields)

Particle accelerators to accelerate sub-Particle accelerators to accelerate sub-atomic particles to nearly the speed of lightatomic particles to nearly the speed of light

Electric generators- made with Electric generators- made with superconducting wire: They have a 99% superconducting wire: They have a 99% efficiency and have about half the size of efficiency and have about half the size of conventional generators.conventional generators.

Really fast computers- In "petaflop" Really fast computers- In "petaflop" computers. A petaflop is a thousand-trillion computers. A petaflop is a thousand-trillion floating point operations per second. floating point operations per second. Today's fastest computing operations have Today's fastest computing operations have only reached "teraflop" speeds.only reached "teraflop" speeds.

Applications soon to Applications soon to come… come…

Stabilizing momentum wheel (gyroscope) for earth-Stabilizing momentum wheel (gyroscope) for earth-orbiting satellites- can reduce friction to near zeroorbiting satellites- can reduce friction to near zero

Superconducting x-ray detectors and superconducting Superconducting x-ray detectors and superconducting light detectors - able to detect extremely weak amounts light detectors - able to detect extremely weak amounts of energy.of energy.

Superconducting digital router- for high-speed data Superconducting digital router- for high-speed data communications up to 160 Ghzcommunications up to 160 Ghz

Power plants use to reduce greenhouse gas emissionsPower plants use to reduce greenhouse gas emissionsAdvancements depend to a great degree on Advancements depend to a great degree on

advancements in the field of cryogenic cooling or advancements in the field of cryogenic cooling or finding more high-temperature superconductorsfinding more high-temperature superconductors

Rotational magnetism Rotational magnetism

Also known as spin stabilized magnetic Also known as spin stabilized magnetic levitation levitation

Happens when the forces acting on the Happens when the forces acting on the levitating object- gravitational, magnetic, levitating object- gravitational, magnetic, and gyroscopic- are in equilibriumand gyroscopic- are in equilibrium

Earnshaw’s theorem says it is impossibleEarnshaw’s theorem says it is impossible

Super LevitronSuper Levitron

Two opposing neodymium-iron-boron permanent magnets.Two opposing neodymium-iron-boron permanent magnets. original invention by Roy Harrigan and patented in 1983. original invention by Roy Harrigan and patented in 1983. He didn’t known about Earnshaw’s theorem which many thought He didn’t known about Earnshaw’s theorem which many thought

said such an invention was impossible. said such an invention was impossible. The rotation of a spinning object’s axis of spin creates a toriod of The rotation of a spinning object’s axis of spin creates a toriod of

genuine stability in a way that does not violate Earnshaw’s genuine stability in a way that does not violate Earnshaw’s theorem, but that went completely unpredicted by physicists for theorem, but that went completely unpredicted by physicists for more than a century. more than a century.

The top remain levitating in a central point in space above the The top remain levitating in a central point in space above the base where the forces acting on the top- gravitational, magnetic, base where the forces acting on the top- gravitational, magnetic, and gyroscopic- are in equilibriumand gyroscopic- are in equilibrium

Stops due to air resistanceStops due to air resistance

http://www.levitron.com/images/levitron.mpghttp://www.levitron.com/images/levitron-drbob.mpg

Why it works Why it works

““The principle is that two similar poles The principle is that two similar poles (e.g., two north's) repel, and two (e.g., two north's) repel, and two different poles attract, with forces that different poles attract, with forces that are stronger when the poles are are stronger when the poles are closer. There are four magnetic closer. There are four magnetic forces on the top: on its north pole, forces on the top: on its north pole, repulsion from the base's north and repulsion from the base's north and attraction from the base's south, and attraction from the base's south, and on its south pole, attraction from the on its south pole, attraction from the base's north and repulsion from the base's north and repulsion from the base's south. Because of the way the base's south. Because of the way the forces depend on distance, the north-forces depend on distance, the north-north repulsion dominates, and the north repulsion dominates, and the top is magnetically repelled. It hangs top is magnetically repelled. It hangs where this upward repulsion balances where this upward repulsion balances the downward force of gravity, that is, the downward force of gravity, that is, at the point of equilibrium where the at the point of equilibrium where the total force is zero.”total force is zero.”

How to get it to WorkHow to get it to Work

Correct magnetic strengthsCorrect magnetic strengths Mass of the top must be Mass of the top must be

right within .5%right within .5% Magnets are temperature Magnets are temperature

dependent, weaker in dependent, weaker in warmer temperatureswarmer temperatures

Correct spinning rate (not Correct spinning rate (not too fast or slow)too fast or slow)

Must be introduced onto a Must be introduced onto a small stabile region only small stabile region only millimeters wide and highmillimeters wide and high

ReferencesReferences

http://www.physics.ucla.edu/marty/levitron/spinstab.pdfhttp://www.physics.ucla.edu/marty/levitron/spinstab.pdf http://www.superconductors.org/uses.htmhttp://www.superconductors.org/uses.htm http://www.popsci.com/popsci/how20/be199aa138b84010vgnvcmhttp://www.popsci.com/popsci/how20/be199aa138b84010vgnvcm

1000004eecbccdrcrd.html1000004eecbccdrcrd.html http://www.chem.yale.edu/~chem125/levitron/levitron.htmlhttp://www.chem.yale.edu/~chem125/levitron/levitron.html http://science.howstuffworks.com/magnet3.htmhttp://science.howstuffworks.com/magnet3.htm http://www.howstuffworks.com/electromagnet.htmhttp://www.howstuffworks.com/electromagnet.htm http://en.wikipedia.org/wiki/Magnethttp://en.wikipedia.org/wiki/Magnet http://en.wikipedia.org/wiki/Electromagnethttp://en.wikipedia.org/wiki/Electromagnet http://en.wikipedia.org/wiki/Magnetic_levitationhttp://en.wikipedia.org/wiki/Magnetic_levitation http://my.execpc.com/~rhoadley/maglev.htmhttp://my.execpc.com/~rhoadley/maglev.htm http://www.hfml.science.ru.nl/hfml/froglev.htmlhttp://www.hfml.science.ru.nl/hfml/froglev.html