1. Two charged concentric spherical shells have radii 10.0cm and 15.0cm. The charge on the inner shell is 4.00X10^-8C, and that on the outer shell is 2.00X10^-8C. Find the electric field (a) at r = 12.0cm and (b) at r = 20.0cm.
2, Two Large metal plates of area 1.0 m^2 face each other. They are 5.0 cm apart and have equal but opposite charges on their inner surfaces. If the magnitude E of the electric field between the plates is 55 N/C, what is the magnitude of the charge on each plate? Neglect edge effects.