Consider a uniform electric field `bar(E)=3 xx10^(3) NC^(-1)`. What is the flux of this field through a square of 10 cm on a side whose plane is parallel to the YZ plane?

Explanation

Given, `bar(E)=3 xx 10^(3) NC^(-1)` (field is along positive x-axis)
Surface area of square, `S=(10xx10^(-2))(10xx10^(-2))=10^(-2) m^(2)`.
When plane of the square is parallel to yz-plane its area vector points towards +ve axis.
So `theta=0^(@)`.
`:.` Flux through square, `phi=ES cos theta=3 xx 10^(3)xx10^(-2) xxcos 0^(@)implies phi =30 NC^(-1) m^(2)`.