Careful measurement of the electric field at the surface of a black box indicates that the net outward flux through the surface of the box is `8.0 xx 10^3 Nm^2//C`.
(a) What is the net charge inside the box ?
(b) If the net outward flux through the surface of the box were zero, could you conclude that there were no charges inside the box ? Why or Why not ?

Explanation

(a) According to Gauss.s law, net electric flux passing through any closed surface, enclosiri net charge q in vacuum (or free space) is,
`phi = q/epsilon_(0)`
`therefore q = phiepsilon_(0)`
`= 8 xx 10^(3) xx 8.85 xx 10^(-12)`
`therefore q = 7.08 xx 10^(-8)` C
(b) Again, `phi^(.) = q^(.)/epsilon_(0)`
Here, `phi. = 0 rArr q. =0`
Given box might contain equal amount o unlike charges whose net charge is zerc Thus, when q. = 0, it is not necessary that i does not contain any charge.