Question

The electric flux from a cube of edge $l$ is $\varphi$. If an edge of the cube is made $2l$ and the charge enclosed is halved, its value will be :

• A. $4\varphi$
• B. $2\varphi$
• C. $\varphi /2$
• D. $\varphi$

Answer 1

The correct option is C $\varphi /2$

${\varphi }_1=\frac{q}{{ϵ}_0}$

$q^{\prime }=\frac{q}{2}$ and $\varphi$ is independent of dimensions

${\varphi }_2=\frac{q}{2{ϵ}_0}=\frac{{\varphi }_1}{2}$