Question

The electric flux from a cube of edge $l$ is $\varphi$. Its value if edge of cube is made $2l$ and charge enclosed is halved is

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

Answer 1

The correct option is A $\frac{\varphi }{2}$

Given flux from a cube of edge l,
we know $\int E.da=\frac{Qenclose}{{ϵ}_o}$ ( Guass laws )
$\varphi =\frac{Q}{{ϵ}_o}$

As Q is halved
value ${\varphi }_1=\frac{Q}{2{ϵ}_o}$
( $\varphi$ is independent of size of cube )