A long cylindrical aluminum rod of radius 1 mm is surrounded by a copper cylindrical shell of inner radius R₁ and outer radius R₂. The two conductors are separated by an electrical insulator. The rod and the shell carry equal and opposite currents of magnitude I that are distributed uniformly across their volumes. Determine the magnitude of the magnetic field at point A located at a distance r > R₂ from the axis of the rod.

Consider a closed loop that surrounds a long coaxial cable consisting of cylinder-shaped conductors spaced apart by an insulator. The anticlockwise line integral ∲B•dl around this loop is 1.27 × 10^-2 T•m. Determine the value of the clockwise line integral ∲B•dl.

Calculate the line integral of B̂•dŝ between points A and B.

Given the line integral value of B•ds as 2.05 × 10 ^-5 T•m around the closed path in the provided diagram, determine the magnitude and direction (into or out of the figure) of the current I ₄ responsible for generating the magnetic field B.