Finding Closed Surfaces for Point Charge at Origin

[august_2007]

If there's a point charge at the origin, I want to find two closed surfaces such that the flux through one of them is zero while the other is not.

I know this may seem trivial but I just want to make sure I understand the question.

My answer would be that to get a zero flux, the closed surface must NOT enclose the charge at the origin while for the non-zero flux, the surface must enclose the charge; is this OK?

 

[dx]

Yes.

 

[astrokreng]

Yes, that is correct. In order to have a zero flux, the closed surface must not enclose the point charge at the origin. This is because the flux is a measure of the electric field passing through a given surface. If the surface does not enclose the charge, then there is no electric field passing through it, resulting in a zero flux. For the non-zero flux, the closed surface must enclose the charge, as this allows for the electric field to pass through the surface and contribute to the flux. It is important to note that the size and shape of the closed surfaces can vary, as long as they meet the conditions of enclosing or not enclosing the point charge.