# Coaxial cable

A coaxial cable consists of an inner solid cylindrical wire of radius $2 \, \text{mm}$ and an outer conducting hollow cylinder of radius $4 \, \text{mm}$, which each carry a current of magnitude $100 \, \text{mA}$. If the currents travel in opposite directions, what is the magnitude of the magnetic field outside of the cable a distance of $1 \, \text{cm}$ measured perpendicularly from the central axis of the inner wire?

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