The discussion focuses on deriving the magnetic field on the axis of a circular current loop and a rotating charged disc. The magnetic field for the circular loop is established as B = (μ₀ I a²)/(2(a² + z²)^(3/2)) in the z-direction. Participants explore the surface current density for the rotating disc, leading to an integral for the magnetic field, but face challenges in evaluating it due to the complexity introduced by the r³ term. Suggestions for solving the integral include using substitutions and integration by parts, with a focus on simplifying the expression for limits as z approaches infinity. The conversation also touches on calculating the field for a spinning ring with inner and outer radii, emphasizing the importance of careful manipulation of terms to recover the original magnetic field expression.