My topic has been changed to Magnetic Levitation.
by Brandon Siegenfeld
Magnetic Levitation:
Magnet Levitation means to use magnetic fields to suspend an object (written by me)
external image Diamagnetic_graphite_levitation.jpg
(from Wikipedia)

Basics:

What is a magnet?
To understand magnet levitation, one must understand how magnets work. A magnet is a material that exerts a magnetic field. These magetic fields are created by the protons and electrons within in an object. However the orbits of the electrons must be synchronized (orbiting in the same direction) in order to generate any net amount of magnet field. For example in a regular non magnetic objects the electron orbits are not synchronized this causes most of the electrons and protons to cancel each other creating a magnetic field of close to zero. The reason why solids and metals make such great magnets is that solids retain their shape so their electron orbits can remain synchronized. Metals make great magnets because their electrons freely move throughout the metal allowing them to be easily synchronized. (written by me)

Electromagnet:
An electromagnet is similar to a regular magnet, the main difference is that an electric current creates the magnetic field from the flow of electrons in the wire. This also works the other way around too. Moving a wire through an electric field will create a current. This is shown by the equation
F= ILB (sin theta)
F=Force
I=Current
L=length of wire in field
B=Magnetic field
This is an important equation because with it we can determine the force an electromagnet will exert on an object. (written by me from in class material)
This is shown by faradays law which is discussed below… Sorry the pictures didn't show up.

There are two basic principles in dealing with the concept of magnetic levitation. The first law that is applied was created by Michael Faraday. This is commonly known as Faraday’s Law.


Figure 1. Michael Faraday


This law states that if there is a change in the magnetic field on a coil of wire, there is seen a change in voltage. Taking that a bit further, it could be said that if there was a change in voltage, then there would be a change in magnetic field. This occurs in the coil when there is a current induced as a result of that change in voltage. From Figure 2 below it is illustrated that the change in the magnetic field produces a current.


Figure 2. Induced Current from Change in Magnetic Field


For the purposes of magnetic levitation the ability to change the strength of a magnetic field by just changing the current is powerful. If there is a need for more of a force, then sending more current through a coil of wires will produce more of a greater magnetic force.
The direction of the forces created by Faraday’s Law was discovered by a man named Heinrich Lenz. His theory states that “the emf induced in an electric circuit always acts in such a direction that the current it drives around the circuit opposes the change in the magnetic flux which produces the emf.”[i] In other words, this is stating that if there was a current that was created in a coil of wires, then the magnetic field that is being produced will be perpendicular the current direction.


Figure 3. Heinrich Lenz


The application that this has on magnetic levitation is that this will allow the direction of the magnetic field to be predictable and thus a set up can be created for a specific purpose to maximize the force that is created. This has direct application to the rail gun which will be described later.


Figure 4. Perpendicular Force from Induce Current


From Figure 4 above, it is illustrated that there is a coiled wire around the cylinder. Inside that coiled wire is a current that is traveling from left to right. The resulting magnetic force from that current is shown to be perpendicular to the current and is traveling from bottom to top.

(from http://www.calvin.edu/~pribeiro/courses/engr302/Samples/vandyke-Magnetic%20Levitation%20-%20Report.doc by Kevin J. Van Dyke)
Earnshaw theorem-A theorem due to Samuel Earnshaw proves that it is not possible to achieve static levitation using any combination of fixed magnets and electric charges. Static levitation means stable suspension of an object against gravity. There are, however, a few ways of to levitate by getting round the assumptions of the theorem.
(from http://www.hfml.kun.nl/levitation-possible.html written by Philip Gibbs and Andre Geim)



Types of Magnetic Levitation-

Rotating Metal induce magnet force-
(from youtube)

Superconductor Levitation-
(from youtube)
This shows how superconductor can be easily magnetized by an external magnet. It also goes into further depth on some superconducting magnet phenomena, and some of the laws governing superconductors and magnets.
(written by me)

Diamagnetism
A diamagnetic substance is one whose atoms have no permanent magnetic dipole moment. When an external magnetic field is applied to a diamagnetic substance such as bismuth or silver a weak magnetic dipole moment is induced in the direction opposite the applied field. All materials are actually diamagnetic, in that a weak repulsive force is generated by in a magnetic field by the current of the orbiting electron. Some materials, however, have stronger paramagnetic qualities that overcome their natural diamagnetic qualities. These paramagnetic materials, such as iron and nickel, have unpaired electrons.
Diamagnetic Levitation
Diamagnetic Levitation occurs by bringing a diamagnetic material in close proximity to material that produces a magnetic field. The diamagnetic material will repel the material producing the magnetic field. Generally, however, this repulsive force is not strong enough to overcome the force of gravity on the Earth's surface. To cause diamagnetic levitation, both the diamagnetic material and magnetic material must produce a combined repulsive force to overcome the force of gravity. There are a number of ways to achieve this:
Placing Diamagnetic Material in Strong Electromagnetic Fields
Modern Electromagnets are capable of producing extremely strong magnetic fields. These electromagnets have been used to levitate many diamagnetic materials including weakly diamagnetic materials such as organic matter. A popular educational demonstration involves the placement of small frogs into a strong static electromagnetic field. The frog, being composed of primarily water, acts as a weak diamagnet and is levitated.


Placing Diamagnetic Material in Strong Magnetic Fields
Advancements in the development of permanent magnets and diamagnetic materials such as pyrolytic graphite have produced a simple method of diamagnetic levitation by simply placing a thin piece of pyrolytic graphite over a strong rare-earth magnet. The pyrolytic graphite is levitated above the magnet.


Placing Magnetic Material in Strong Diamagnetic Fields
Developments in superconducting materials have produced an easy and dramatic method of demonstrating diamagnetic levitation. A superconductor will not allow a magnetic field to penetrate its interior. It causes currents to flow that generate a magnetic field inside the superconductor that balances the field that would have otherwise penetrated the material. By placing a strong permanent magnet above a superconductor, the magnet will levitate.


Placing Magnetic Material in Diamagnetic Fields with a Biasing Magnet
The last method, and most easily duplicated by the average individual, uses a combination of readily available rare-earth magnets and diamagnetic material such as carbon graphite or bismuth. Through the use of a biasing or compensating magnet, a small rare-earth magnet can be levitated above a piece of diamagnetic material. For added stability, the small magnet is generally placed between two pieces of diamagnetic material. Below is a diagram of this method:




From (http://www.rare-earth-magnets.com/magnet_university/magnetic_levitation.htm)

Below is an example of a diamagnetic material being levitated
Frog being levitated, pity the frog-
(from youtube)

Servomechanics- same as EMS or Electro magnetic suspension it is is discussed below under Maglev train
Other magnetic levitation methods- These methods will not be discussed in depth because the level of physics is beyond what was intended to be discussed. Rotational stability- spinning a magnet in a ring of magnets.Oscillating electromagnetic fields. Strong focusing.

Note- There are probably other forms of magnetic levitation due to the complexity of this area of physics and the many uses.
(written by me, mainly from http://en.wikipedia.org/wiki/Magnetic_levitation)
Applications-
Maglev Train- These trains use magnets to levitate them off the rails eliminating any need for wheels, thereby greatly reducing friction. Current designs for these trains come in three forms: electromagnetic suspension (EMS), electrodynamic suspension (EDS), and stabilized permanent magnet suspension (SPM).
EMS usually uses a magnet to attract the train upwards counteracting gravity, by attracting it against gravity versus repelling it the train gains side to side stability. This magnet is then set to turn off if it gets too close to the magnet and turn on if it moves too far away.
EDS is when both the train and the rails produce a magnetic field. The train uses either permanent or electromagnets to generate a field. Whereas the rails use the current in the power lines to create a magnetic field as shown by the equation F=ILB. At slower speeds this system does need wheels.
SPM uses permanent magnets put on both the train and the rails. These magnets are oposite poles so that they repel each other. To prevent the train from derailing electromagnets help guide the train. This system uses the least amount of energy because it does not have to provide constant levitation energy.However this technology is not commercially available yet.

Propulsion systems usually use electromagnets aligned along the rails which attract and repel the train foward. This is done with the use of AC which is synchronized with the speed of the train so that it will move foward.

An additional feature that can be utilized is using an evacuated tunnel for a train, which basically means a vaccuum tunnel. This increases the efficiency of these trains tremendously

There is also research being done on using superconductors for levitation, the use of this can be seen in one of the videos above discussing superconductor levitation. However this is not in the fully practical stages yet due to the extremely cold temperatures they must operate at.

Current maglev trains are in use in China, Japan, Germany, and maybe a few others. Research is being done in many countries and many are considering maglev projects. The main reason that the maglev trains are not extremely popular yet is that they are not economical, even though they have low upkeep and operational costs. This is because of their high initial investment which for many of the current maglevs will never be payed off.

(written by me sources http://www.appliedlevitation.com/technology.shtml,http://www.magnet.fsu.edu/education/tutorials/slideshows/maglev/index.html, http://www.appliedlevitation.com/, http://www.maglev2000.com/works/how.html, http://en.wikipedia.org/wiki/Maglev_(transport))


Technology

Pros

Cons

EMS (Electromagnetic suspension)
Magnetic fields inside and outside the vehicle are less than EDS; proven, commercially available technology that can attain very high speeds (500 km/h); no wheels or secondary propulsion system needed
The separation between the vehicle and the guideway must be constantly monitored and corrected by computer systems to avoid collision due to the unstable nature of electromagnetic attraction; due to the system's inherent instability and the required constant corrections by outside systems, vibration issues may occur.

EDS (Electrodynamic)
Onboard magnets and large margin between rail and train enable highest recorded train speeds (581 km/h) and heavy load capacity; has recently demonstrated (December 2005) successful operations using high temperature superconductors in its onboard magnets, cooled with inexpensive liquid nitrogen
Strong magnetic fields onboard the train would make the train inaccessible to passengers with pacemakers or magnetic data storage media such as hard drives and credit cards, necessitating the use of magnetic shielding; limitations on guideway inductivity limit the maximum speed of the vehicle; vehicle must be wheeled for travel at low speeds.

Inductrack System (Permanent Magnet EDS)
Failsafe Suspension - no power required to activate magnets; Magnetic field is localized below the car; can generate enough force at low speeds (around 5 km/h) to levitate maglev train; in case of power failure cars slow down on their own safely; Halbach arrays of permanent magnets may prove more cost-effective than electromagnets
Requires either wheels or track segments that move for when the vehicle is stopped. New technology that is still under development (as of 2008) and as yet has no commercial version or full scale system prototype.
(from wikipedia)


(from youtube)
Particle accelerators- These operate on some of the similar propulsion principles used in maglev trains. They use AC to attract and repel a charged particle, this is synchronized with the particles speed so the attractive force is always in front of the particle pulling it along. Whereas the repeling force is always behind it pushing it. These are the main systems used in linear accelerators. Circular accelerators use the same concept, however they also require a centripetal force inward or else the particle would just go in a strait line like the linear accelerators. The inward force can be generated either by attraction or repulsion.
(written by me, no source just knowledge from project awhile ago)

Questions:
Which type of magnetic levitation system do you think will be most likely to be applied in the future?
Why does the frog "float" (watch frog video video)?
Why do superconductors easily take on magnetic charges (think of superconductor properties)?
Why do you need to use AC (alternating current) to attract/repel the train foward and not DC (direct current)?
(If anyone knows, from Angels and Demons) Can you really suspend antimatter in a magnetic field? Why?
Links/Sources:
http://www.maglev2000.com/works/how.html
http://www.appliedlevitation.com/
http://www.appliedlevitation.com/technology.shtml,http://www.magnet.fsu.edu/education/tutorials/slideshows/maglev/index.html

http://en.wikipedia.org/wiki/Maglev_(transport)
http://www.hfml.kun.nl/levitation-possible.html
http://www.calvin.edu/~pribeiro/courses/engr302/Samples/vandyke-Magnetic%20Levitation%20-%20Report.doc

http://en.wikipedia.org/wiki/Magnetic_levitation



Classmate Questions:
Sonia Bansal - What are the non-cost related benefits of Maglev Trains?

Answer- They are better for the environment because they are more efficient then regular trains. They also cut down on noise polution which makes it easier to place them in populated areas without disturbing the citizens in that area. Also Maglev Trains are a lot faster then normal trains which is a big benefit for commutors. And further research of maglev trains help open up new technological advances to science while also helping to improve current Maglev trains.

Robert Lopez - How can the average person utilzie this in everyday life?

Answer-No unless they ride on a maglev train or they use one of those levitating toy globes. No other current applications are out yet at least for the average person.

James Song- What effects does the levitation have on the frog?

Answer- Strong magnetic fields can cause non normal patterns of blood flow, perhaps from the iron content. It may also cause nerve excitablility. A freaked out frog. Other than that not too much.

Kevin Norris - How do you correct for instabilities in EMS-based trains?

Answer-There are sensors that will activate certain magnets if the train moves outside a certain distance of its track. This will help account for non normal circumstances like wind, rain, etc. that could throw the train off its track.

Sam Edwards - How does the flux trapping effect work?

Answer- This was an experiment that contradicted the meisner effect that included the trapping of permanent magnets by a superconductor.

William Chan - What are the negative aspects of the Maglev Train?

Answer-They as stated above are not really cost effective yet. They are expensive. And many of the forms of maglev are not fully perfected yet.

Greg Sturm - Could a magnetic levitator be thrown off by external magnetic forces, such as the one from the Earth?

Answer- The Earth's magnetic force is way to weak to throw off a maglev train, also any impact the field would have would be corrected for. However external magnetic forces would effect the train and that is the point of having the trains have sensors to activate certain magnets to keep the train on track.

Ari Horowitz - How can super conductors be used for Maglev trains?

Answer- Superconductors as shown in the video will actually mirror the poles of a magnet near by which creates a repulsive force, this is because the electrons more freely move throughout the conductor. This can be used to levitate the train, the other option would be for the superconductor to be used as wiring for the electromagnets and since superconductors have little resistance you could in theory increase efficiency. The problems come in when you have to figure out how to keep the conductors at cold temperatures.

Douglas Chin - So is a railgun powered by magnetic levitation then?

Answer-No that is based off the Lorenz force which causes the projectile to accelerate.