Question

Choose the incorrect statement

$\left(a\right)$ The electric lines of force entering into a Gaussian surface provide negative flux.
$\left(b\right)$ A charge $q$ is placed at the centre of a cube. The flux through all the faces will be the same.
$\left(c\right)$ In a uniform electric field net flux through a closed Gaussian surface containing no net charge is zero.
$\left(d\right)$ When electrical field is parallel to a Gaussian surface, it provides a finite non-zero flux.

Choose the most appropriate answer from the option given below

• A. $\left(d\right)$ Only
• B. $\left(c\right)$ and $\left(d\right)$ Only
• C. $\left(b\right)$ and $\left(d\right)$ Only
• D. $\left(a\right)$ and $\left(c\right)$ Only

Answer 1

The correct option is A $\left(d\right)$ Only

$\left(a\right)$ Electric flux is defined as $\varphi =\overrightarrow{E}.\overrightarrow{A}$
When electric field of lines are entering into the gaussian surface and le between electric field and areal vector is obtuse. Hence flux is negative.

$\left(b\right)$ A charge $q$ is placed at the centre of a cube. The flux through all the faces will be the same and is equal to $\frac{q}{6{ϵ}_0}$

$\left(c\right)$ From Gauss law, electric flux is given by $\varphi =\frac{q_{in}}{{ϵ}_0}$. If $q_{in}=0$, electric flux is zero.

$\left(d\right)$ As electric flux is defined as $\varphi =\overrightarrow{E}.\overrightarrow{A}$
If electric field lines are parallel to gaussian surface, angle between $\overrightarrow{E}\&\overrightarrow{A}$ is ${90}^{\circ },$ $\varphi =0$

hence only $\left(d\right)$ is incorrect