Question

Two spherical shells have a common center. A -1.9 10-6 C charge is spread uniformly over the inner shell, which has a radius of 0.050 m. A +5.5 10-6 C charge is spread uniformly over the outer shell, which has a radius of 0.15 m. Find the magnitude and direction of the electric field at the following distances (measured from the common center). (b) 0.10 m magnitude

Answer 1

   Givne data

   inner sphere charge q1 = - 1.9*10^-6 C, radius r1 = 0.050 m

   outer sphere charge q2 = +5.5*10^-6 C, radius r2 = 0.15 m

   Electraic field at a point r form the reference point (centre of s sphere ) i s

       E = k *Q/r^2

   now the point 0.10 m is inside the outer sphere and out side the inner sphere

       The electric field E at 0.10 m is

       E = kq1/r1^2
          = 9*10^9*-1.6*10^-6 / 0.10^2
          = - 1440000 N/C

     - ve indicates field is directed towards the centre.

   because electric field lines are originated form + ve charge and towards the - ve charges