1)Three electric insulated point charges are forming an equilateral triangle with side a.

a.) Find electric field at the center of this triangle.

b.) What will be the magnetic field at the center of the same triangle, when charges are moving along its sides with constant velocity v in clockwise direction and are exactly in the middle between two consequent corners?

2) A metal ring of radius r carries uniformly distributed along its circumference charge Q. Define the electric field in the center of this ring and on its axis (assume that the distance form some point on the axis to the center of the ring is a).

3) A solid, insulating sphere of radius (a) has a uniform charge density p and a total charge +Q. Find the magnitude of the electric fiel in the regions ra. Draw the schematic graph of electric field ( E vs. r).