Superconductors Part 2

Alan Cai

August 11, 2023

In addition to the ability to conduct electricity without resistance, superconductors also possess unique magnetic capabilities. Superconductors are validated upon the demonstration of the Meissner effect, which is unique to superconductors. Whilst transitioning to a superconductor amid temperature decrease past the necessary point, the superconductive materials expel the internal magnetic fields resulting in a levitation effect.

Magnetism is a property exhibited by materials containing electric charges in motion. It is one of the two components, along with electrostatics, forming the fundamental force electromagnetism. Electromagnetism is one of the four fundamental forces of nature and encompasses interactions between charged particles. The other three fundamental forces are strong interaction, weak interaction, and gravity. Strong interaction is a force that binds quarks and composite hadrons together. Quarks bound together form neutrons, protons, and other composite particles known as hadrons. Strong force also holds together positively charged protons in atomic nuclei and prevents electromagnetic force from separating the same-charged particles. Interestingly, the vast majority of the mass in a proton is given by energy contained in strong force, with quarks making up the remaining small fraction of mass. The mass-energy equivalence, initially pioneered by Albert Einstein which includes his well known equation, e=mc^2, proves the intrinsic relation between mass and energy, between which a connection is delicately intertwined. Weak interaction is an interaction between odd half integer spin fermions and integer spin and energy-carrying bosons. Spin is a form of angular momentum present in all subatomic particles. In weak interaction, fermions exchange bosons. The force is responsible for beta decay. Finally, gravity is a force that acts upon all objects with mass. Gravity is the weakest out of all of the fundamental forces but is capable of interacting over extremely long distances.

Magnetic fields are vector fields generated in the vicinity of a magnet. Magnets can be permanent magnets(such as lodestones) which perennially exhibit a magnetic field or temporary magnets which are magnetized through interaction with a strong magnetic field and gradually fade in electromagnetic capacity over time. Magnets exert the Lorentz force on charged particles, acting perpendicular to the velocity of the particle and the magnetic field. The Lorentz force is given by the equation F = q(E + V x B) where scalar multiplier q is the charge of the particle, F is the Lorentz force, E is the electric field, B is the electric field, and V is the velocity of the particles. All quantities except for charge q are vectors which means they have direction in addition to magnitude.

When superconductors display the Meissner effect, they expel their internal magnetic field. This phenomenon allows the current particles(electrons or holes) to move through the material without inhibition.