Magnetic flux area S is where "B" is the magnitude of the magnetic field (the magnetic flux density) having the unit of Wb/m (tesla), "S" is the area of the surface, and "θ" is the angle between the magnetic field lines and the normal (perpendicular) to S. For a varying magnetic field, we first consider the magnetic flux through an infinitesimal area element dS, where we may consider the field to be constant: A generic surface, S, can then be broken into infinitesimal elements and the total magnetic flux through the surface is then the surface integral From the definition of the
Magnetic flux quantum the value as one goes around the hole/loop and comes to the same starting point. If this is so, then one has magnetic flux quanta trapped in the hole/loop. Due to Meissner effect, the magnetic induction inside the superconductor is zero. More exactly, magnetic field penetrates into a superconductor over a small distance called London's magnetic field penetration depth (denoted and usually ). The screening currents also flow in this -layer near the surface, creating magnetization inside the superconductor, which perfectly compensates the applied field , thus resulting in inside the superconductor. It is important to note that the magnetic