Careful measurements of the electric field at the surface of a box inidcates that the net outward flux through the surface of box is `60xx10^(3) Nm^(2) C^(-1)`. Find (i) the net charge inside the box ? (ii) If the net outward flux through the surface of box were zero, could you conclude that there were no charges inside the box ? Explain your answer.

Explanation

(i) Here, `phi_(E) = 16xx10^(3) Nm^(2) C^(-1)`
Acc. To Gauss theorem `phi_(E) = (q)/(in_(0))`
So `q = phi_(E) xx in_(0) = 16xx10^(3) xx8.85xx10^(-12)`
`= 0.14xx10^(-6) C = 0.14 muC`
(ii) No, we can not say that there are no charges at all inside the box. We can only say that algebraic sum of charges inside the box is zero.