Calculate the electric flux through the rectangle of sides 5 cm and 10 cm kept in the region of a uniform electric field 100 NC-1. The angle θ is 60o. Suppose θ becomes zero, what is the electric flux?
The electric flux
(i) In figure (a), calculate the electric flux through the closed areas A1 and A2.
(ii) In figure (b), calculate the electric flux through the cube
(i) In figure (a), the area A1 encloses the charge Q. So electric flux through this closed surface A1 is Q/ ε . But the closed surface A2 contains no charges inside, so electric flux through A2 is zero.
(ii) In figure (b), the net charge inside the cube is 3q and the total electric flux in the cube is therefore ΦE = 3q/ ε .
Note that the charge -10 q lies outside the cube and it will not contribute the total flux through the surface of the cube.