Ferromagnetism:<br />8<br />Mechanism by which certain materials (such as iron) form permanent magnets.<br />Material that could exhibit spontaneous magnetization: a net magnetic moment in the absence of an external magnetic field.<br />Method:<br />The spin of an electron, combined with its electric charge, results in a magnetic dipole moment and creates a magnetic field.<br />Ferromagnetism only occurs in materials with partially filled shells due to the spin of unpaired electrons in the atomic/molecular electron orbitals<br />Dipoles are randomly oriented in the absence of an external field due to thermal agitation, resulting in zero net magnetic moment. <br />When a magnetic field is applied, the dipoles tend to align with the applied field, resulting in a net magnetic moment in the direction of the applied field. <br />
Diamagnetism<br />10<br />Diamagnetism is the property of an object which causes it to create a magnetic field in opposition to an externally applied magnetic field, thus causing a repulsive effect.<br />Superconductors may be considered to be perfect diamagnets ( = −1), since they expel all fields from their interior due to the Meissen effect.<br />
11<br />Eddy Current:<br /><ul><li>Eddy currents are currents induced in conductors to oppose the change in flux that generated them.
Caused when a conductor is exposed to a changing magnetic field or due to relative motion of the field source and conductor or due to variations of the field with time.
This can cause a circulating flow of electrons, or a current, within the body of the conductor.
These circulating eddies of current create induced magnetic fields that oppose the change of the original magnetic field due to Lenz's law, causing repulsive or drag forces between the conductor and the magnet.</li></ul>Repulsive effects and levitation:<br />In a fast varying magnetic field the induced currents, good conductors exhibit diamagnetic-like repulsion effects on the magnetic field, and hence on the magnet and can create repulsive effects and even stable levitation.<br />Reasonably high power dissipation due to the high currents this entails<br />
Procedure Detailed: Lift<br />13<br />Magnetic materials and systems are able to attract or press each other apart or together with a force dependent on the magnetic field and the area of the magnets, and a magnetic pressure can then be defined.<br />The magnetic pressure of a magnetic field on a superconductor can be calculated by:<br />where Pmag is the force per unit area in Pascal's, B is the magnetic field in teals, and μ0 = 4π×10−7 N·A−2 is the permeability of the vacuum.<br />
Procedure Detailed: Propulsion:<br />15<br />Induced currents/eddy currents<br />The (eddy) current induced in the conductor will oppose the changes in the field and create an opposite field that will repel the magnet (Lenz's law). <br />At a sufficiently high rate of movement, a suspended magnet will levitate on the metal, or vice versa with suspended metal.<br />Guide Magnets:<br />Alternating NSNS bars on both side of inductrack interact with magnets of train. Levitated & propelled<br />
USE<br />16<br />Faster & Smoother than wheeled mass transit systems<br />Shanghai Trains<br />
Difficulties<br />17<br /><ul><li> Narrow region of stability.