An electric point of 6 mill- coulomb is placed in the center of a metallic spherical shell of inner diameter 15 cm and thickness 18 cm. Calculate the electric field at the following distances from the point charge. 10cm, 16cm, 25 cm.
a. The charge is now taken out from the spherical shell and placed outside it at a distance 25cm from the center of the sphere. Calculate the electric field at the center of the spherical shell.