# Magnetic Fields!

**Electricity and Magnetism**Level 3

A nonconducting disk of Radius 5 m has charge density (units C/m^2) of p(r)=2pi*r (at the center there is essentially no charge, and each ring of radius r around the center has charge density per area of 2pi*r). The disk spins at angular velocity 10 rad/s around an axis perpendicular to the plane that the disk is on and through the center of the disk. What is the magnitude of the magnetic field at the center of the disk? Provide your answer to three significant figures (and do not use scientific notation).

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