Question

A solid spherical insulator has radius r = 2.5 cm, and carries a total positive charge q = 8 × 10-10 c distributed uniformly throughout its volume. find the magnitude of the electric field |e| at a radius of 5 cm from the origin (i.e., outside the sphere).

Answer 1

At r = 2R> R The expression for the electric field will be given by: (2R)^2*E=kQ. Where, k=(9*10^9)N.m/C^2, Q=(8*10^-10)C and R=0.025m.  So substituting and clearing, we have that the magnitude of the electric field will be:  E=(9*10^9)*(8*10^-10)/((2*0.025)^2)=2880 N / C.