A uniformly charged ring of radius 10 cm is placed on a nonconducting table. It is found that 3.0 cm above the centroid of the half-ring the potential is V, taking zero potential to be at infinity. How much charge is contained in the half-ring?
A rod bent into the arc of a circle of radius 0.500 m subtends an angle at the center of the circle as shown. Each equals . If the rod is charged uniformly with a total density 0.033 C/m, what is the magnitude of the electric field at ?