(a)The electric field at a point inside the charged sphere is
E = (1/4πεo) * (qr/R3)
or q = [(E * R3)/(k * r)]
Here,E = 40 kN/C = 40 * 103 N/C,R = 1.7 cm = 1.7 * 10-2 m,k = 9 * 109 Nm2/C2 and r = 0.85 cm = 0.85 * 10-2 m
or q = [(40 * 103 * (1.7 * 10-2)3/(9 * 109) * (0.85 * 10-2)]
or q = 2.57 * 10-9 = 2.57 nC
The electric field at a point outside the charged sphere is
E = (1/4πεo) * (q/r2)
or r2 = (kq/E)
or r = (kq/E)
1/2
or r = [(9 * 109) * (2.57 * 10-9)/(40 * 103)]1/2
or r = 2.4 * 10-2 m = 2.4 cm
(b)The net charge on the sphere is 2.57 nC.