Question

Which circle has minimum flux in the following figure?

Answer 1

Answer:

Circle Q

Explanation:

The flux of a field through a surface is given by:

$\Phi = F A cos \theta$

where

F is the field strength

A is the area of the surface

$\theta$ is the angle between the direction of the field and the normal to the surface

In the figure, we see that the 4 surfaces have different orientations, so different angle $\theta$. In the formula, we see that the flux is maximum when $\theta=0^{\circ}$, which occurs when the field is perpendicular to the surface, and the flux is zero when $\theta=90^{\circ}$, (because $cos 90^{\circ}=0$) which occurs when the field is parallel to the surface.

In the figure, we see that circle Q is parallel to the direction of the field, so in this case the field is zero, while in all the other cases is not.

So, the correct answer is

Circle Q