Download - Magnetic Levitation PowerPoint
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