Applications of magnetism
Magnetic Resonance Images (MRI)
These machines can produced up to 7 Tesla to make very good images of the body
Q: How to produce a strong magnetic field ?
A: Build a giant solenoid
Q: What is the problem with producing a strong magnetic field
A: #1 Material cannot stand the magnetic force with the magnetic field; resulting in collapsing the material
#2 High velocity of current running through the solenoid produce a lot of heat. This can result in melting the solenoid if the magnetic field is too strong
- superconductors are very useful because it does not have any resistant with other material
- all superconductors are diamagnetic
Animals such as sharks and turtles can detect Earth magnetic field to know where their position and direction around the globe (Research has not been finished, a few published paper support this theory)
Q: Why do people invent Maglev trains?
A: Less friction than trains with wheels because it does not need wheels to run
- first it levitates using superconductors
Q: Why do we need superconductors to levitate, why can’t we use ferromagnetic material like the train in the demo?
A: The problem with using ferromagnetic material to levitate the train is because ferromagnetic material will tend to want to align itself with the opposing field. Therefore, the train will be unstable moving right and left (i.e. like the train in the demo). The good thing about superconductors is because they are diamagnetic. They will always oppose a magnetic field, so they will not move out of the track trying to align with the field like ferromagnetic materials
- After the train is levitated, the train can move forward by the magnetic coil from the side. These coils can flip from N to S and vice versa to attract and repel against the magnets on the train (the magnets on the train is fixed and cannot be flipped.