(Solution) - A disk of radius R carries a fixed charge density -(2025 Original AI-Free Solution)

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A disk of radius R carries a fixed charge density ? and rotates with angular velocity ?.
(a) Consider a circular strip of radius r and width dr with charge dq. Show that the current produced by this strip dI = (?/2?) dq = ??r dr.
(b) Use your result from part (a) to show that the magnetic field at the center of the disk is B = ½?0??R.
(c) Use your result from part (a) to find the magnetic field at a point on the axis of the disk a distance x from the center.