A conducting sphere of radius 10 cm has an unknown charge if the electric field 20 cm from the centre of the sphere is `1.5 xx10^(3) ` N/C and points radialy inward what is the net charge on the sphere

Explanation

Electric field at a point outside the charged sphere of radius R is,
`E_(0) = (kq)/(r^(2))` (where `r gt R`)
`therefore q = (E_(0) xx r^(2))/(k)`
`=(-1.5 xx 10^(3) xx (0.2)^(2))/(9 xx 10^(9))`
`therefore q = -6.667 xx 10^(-9)` C
(Here `E_(0)` point is radially inward and so it is taken as negative)