1. Tori Johnson and Jenna Wilson
Magnetic Levitation
Tori Johnson and Jenna Wilson

2. What is a magnet?
It is simply an object which produces a magnetic field
North and South are the designations made to describe the two opposite poles
North is attracted to South and repelled by North
South is attracted to North and repelled by South
There are three main types:
- Permanent Magnets
- Soft Magnets
- Electromagnets

3. Permanent Magnets Electrons fill atomic orbitals in pairs
If an orbital is full, then one electron spins upward and the other spins downward (Pauli Exclusion Principle), so their magnetic fields cancel out
If an orbital is not full, then the movement of the electron creates a tiny magnetic field
Atoms with several unpaired orbitals have an orbital magnetic moment

4. 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 the magnet’s center

5. Soft Magnets
These types of magnets do not have a magnetic field of their own
However, when put in the presence of another object’s magnetic field, they are attracted (paramagnetic)
Once the external magnetic field is removed, they return to their nonmagnetic state

6. Electromagnets
The magnetic field is caused by the flow of an electric current
The simplest example is a coiled piece of wire
Using 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

7. Nine Ways to Magnetically Levitate an Object
Mechanical constraint
Direct diamagnetic levitation
Superconductors
Diamagnetically-stabilized levitation
Rotational stabilization
Servo stabilization
Rotating conductors beneath magnets
High-frequency oscillating electromagnetic fields
Translational Halbach arrays and Inductrack

8. Direct Diamagnetic Levitation – How it Works
Diamagnetic materials repel a magnetic field
All materials have diamagnetic properties, but the effect is very weak, and usually overcome by the object‘s paramagnetic or ferromagnetic properties, which act in the opposite manner
By 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)

9. Direct Diamagnetic Levitation – Applications
Water is primarily diamagnetic, so water droplets and objects that contain large amounts of water can be levitated

10. Superconductors
A 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

11. Applications
MagLev Trains- The magnetized coil running along the track, repels the large magnets on the train's undercarriage, allowing the train to levitate
Biomagnetism- in MRI and SQUID (measures slight magnetic fields)
Particle accelerators to accelerate sub-atomic particles to nearly the speed of light
Electric 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.

12. Applications soon to come…
Stabilizing momentum wheel (gyroscope) for earth-orbiting satellites- can reduce friction to near zero
Superconducting 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 Ghz
Power plants use to reduce greenhouse gas emissions
Advancements depend to a great degree on advancements in the field of cryogenic cooling or finding more high-temperature superconductors

13. 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
Earnshaw’s theorem says it is impossible

14. Super Levitron Two opposing neodymium-iron-boron permanent magnets.
original invention by Roy Harrigan and patented in 1983.
He didn’t known about Earnshaw’s theorem which many thought said such an invention was impossible.
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 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 equilibrium
Stops due to air resistance

15. 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.”

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

17. References http://www.physics.ucla.edu/marty/levitron/spinstab.pdf