Question

The electric flux from a cube of edge $l$ is $\varphi$ in an enclosed charge. If the edge of the cube is made $\frac{2}{3}l$ and the charge enclosed in the cube is doubles, then the elctric flux value will be

• A. $4\varphi$
• B. $2\varphi$
• C. $\frac{\varphi }{2}$
• D. $\varphi$

Answer 1

Answer: (B)

According to Gauss's law, the electric flux through a closed surface is Electric flux, $\varphi =\frac{Q}{{\epsilon }_0}\dots$ (i)
Electric flux through a closed surface does not depend on the dimensions of closed surface, it depends only the amount of charge enclosed by the closed surface.
According to question,
$Q^{\prime }=2Q$
$\Rightarrow {\varphi }^{\prime }=\frac{Q^{\prime }}{{\epsilon }_0}=\frac{2Q}{{\epsilon }_0}=2\varphi [$ using Eq. (i) $]$