An isolated sphere of radius 5cm is charged to a potential of 159 Kv (Kilovoits). Find the electrostatic force per unit area of the surface.
[Hint: Force per unit area `=(sigma^(2))/(2epsi_(0))and V =(Q)/((4piepsi_(0)r))= (4pir^(2)sigma)/(4piepsi_(0)r)=(rsigma)/(epsi_(0))]`
