What is the Meissner effect? Explain.

(N/A) The Meissner effect is the phenomenon where a superconductor, when cooled below its critical temperature $(T_c)$ in the presence of an external magnetic field, expels all magnetic flux from its interior.
As the material transitions into the superconducting state, it develops surface currents that create an internal magnetic field exactly equal and opposite to the applied external magnetic field.
Consequently, the net magnetic field inside the superconductor becomes zero $(B = 0)$.
This property makes superconductors perfect diamagnets, as they exhibit a magnetic susceptibility $(\chi)$ of $-1$.