Magnetic LevitationTori Johnson and Jenna Wilson

What is a magnet?It is simply an object which produces a magnetic fieldNorth and South are the designations made to describe the two opposite polesNorth is attracted to South and repelled by NorthSouth is attracted to North and repelled by SouthThere are three main types:- Permanent Magnets- Soft Magnets- Electromagnets

Permanent MagnetsElectrons fill atomic orbitals in pairsIf an orbital is full, then one electron spins upward and the other spins downward (Pauli Exclusion Principle), so their magnetic fields cancel outIf an orbital is not full, then the movement of the electron creates a tiny magnetic fieldAtoms with several unpaired orbitals have an orbital magnetic moment

Permanent MagnetsIn metals, the orbital magnetic moment causes nearby atoms to align in the same direction, creating a ferromagnetic metalThe strength of the magnetic field decreases inversely with the cube of the distance from the magnets center

Soft MagnetsThese types of magnets do not have a magnetic field of their ownHowever, 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

ElectromagnetsThe magnetic field is caused by the flow of an electric currentThe simplest example is a coiled piece of wireUsing the right hand rule, it is possible to determine the direction An advantage over permanent magnets is that the magnetic field strength can be changed by changing the current

Nine Ways to Magnetically Levitate an ObjectMechanical constraintDirect diamagnetic levitationSuperconductorsDiamagnetically-stabilized levitationRotational stabilizationServo stabilizationRotating conductors beneath magnetsHigh-frequency oscillating electromagnetic fieldsTranslational Halbach arrays and Inductrack

Direct Diamagnetic Levitation How it WorksDiamagnetic materials repel a magnetic field All materials have diamagnetic properties, but the effect is very weak, and usually overcome by the objects paramagnetic or ferromagnetic properties, which act in the opposite mannerBy surrounding a diamagnetic material with a magnetic field, it can be held in a stationary position (the magnetic force is strong enough to counteract gravity)

Direct Diamagnetic Levitation ApplicationsWater is primarily diamagnetic, so water droplets and objects that contain large amounts of water can be levitatedhttp://www.hfml.ru.nl/pics/Movies/frog.mpg

SuperconductorsA superconductor is an element, inter-metallic alloy, or a compound that will conduct electricity without resistance below a certain temperature.Resistance produces losses in energy flowing through the material.In a closed loop, an electrical current will flow continuously in a superconducting material. Superconductors are not in widespread use due to the cold temperatures they must be kept at Highest Tc found 150K

ApplicationsMagLev Trains- The magnetized coil running along the track, repels the large magnets on the train's undercarriage, allowing the train to levitateBiomagnetism- in MRI and SQUID (measures slight magnetic fields)Particle accelerators to accelerate sub-atomic particles to nearly the speed of lightElectric generators- made with superconducting wire: They have a 99% efficiency and have about half the size of conventional generators.Really fast computers- In "petaflop" computers. A petaflop is a thousand-trillion floating point operations per second. Today's fastest computing operations have only reached "teraflop" speeds.

Applications soon to come Stabilizing momentum wheel (gyroscope) for earth-orbiting satellites- can reduce friction to near zeroSuperconducting x-ray detectors and superconducting light detectors - able to detect extremely weak amounts of energy.Superconducting digital router- for high-speed data communications up to 160 GhzPower plants use to reduce greenhouse gas emissionsAdvancements depend to a great degree on advancements in the field of cryogenic cooling or finding more high-temperature superconductors

Rotational magnetism Also known as spin stabilized magnetic levitation Happens when the forces acting on the levitating object- gravitational, magnetic, and gyroscopic- are in equilibriumEarnshaws theorem says it is impossible

Super LevitronTwo opposing neodymium-iron-boron permanent magnets.original invention by Roy Harrigan and patented in 1983. He didnt known about Earnshaws theorem which many thought said such an invention was impossible. The rotation of a spinning objects axis of spin creates a toriod of genuine stability in a way that does not violate Earnshaws theorem, but that went completely unpredicted by physicists for more than a century. The top remain levitating in a central point in space above the base where the forces acting on the top- gravitational, magnetic, and gyroscopic- are in equilibriumStops due to air resistancehttp://www.levitron.com/images/levitron.mpghttp://www.levitron.com/images/levitron-drbob.mpg

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

How to get it to WorkCorrect magnetic strengthsMass of the top must be right within .5%Magnets are temperature dependent, weaker in warmer temperaturesCorrect spinning rate (not too fast or slow)Must be introduced onto a small stabile region only millimeters wide and high

Referenceshttp://www.physics.ucla.edu/marty/levitron/spinstab.pdfhttp://www.superconductors.org/uses.htmhttp://www.popsci.com/popsci/how20/be199aa138b84010vgnvcm1000004eecbccdrcrd.htmlhttp://www.chem.yale.edu/~chem125/levitron/levitron.htmlhttp://science.howstuffworks.com/magnet3.htmhttp://www.howstuffworks.com/electromagnet.htmhttp://en.wikipedia.org/wiki/Magnethttp://en.wikipedia.org/wiki/Electromagnethttp://en.wikipedia.org/wiki/Magnetic_levitationhttp://my.execpc.com/~rhoadley/maglev.htmhttp://www.hfml.science.ru.nl/hfml/froglev.html