Question

The net outward flux through the surface of a cube is 16kNm2/C.
(a) What is the net charge inside the cube?

(b) If the net outward flux through the surface of the cube were zero, is it correct
to say that there were no charges inside the box?
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Answer 1

Heya....

a) Net outward flux through the surface of the box, Φ = 8.0 × 103 N m2/C

For a body containing net charge q, flux is given by the relation,

∈0 = Permittivity of free space

= 8.854 × 10−12 N−1C2 m−2

q = ∈0Φ

= 8.854 × 10−12 × 8.0 × 103

= 7.08 × 10−8

= 0.07 μC

Therefore, the net charge inside the box is 0.07 μC.

(b) No

Net flux piercing out through a body depends on the net charge contained in the body. If net flux is zero, then it can be inferred that net charge inside the body is zero. The body may have equal amount of positive and negative charges.