Electric flux (positive, negative, or zero?)

[rwrem]

Homework Statement

Imagine a positive point charge on the left side of the picture and an area defined by a loop on the right. I was asked to draw and label the area vector and sketch the electric field lines due to the point charge, which I did. The next questions asks:

Is the electric flux through the loop due to the charge positive, negative, or zero?

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My inclination is to say positive because the direction the area vector points is the same as the direction of the electric field lines.

But, the materials I've seen so far talks about the the electric flux flowing into or out of some enclosed box or sphere and never really mentions that an electric flux can be positive or negative. I can understand where you could get a zero total flux answer, where the flux flowing into and out of a box is the same, but am not sure how that relates to the situation above.

Again, due to missing some classes due to swine flu, I may have missed some fundamental explanations...

 

[rwrem]

So, I guess it's positive, then? Seems logical to me, but I'm surprised no one has commented yet...

 

[tomcue]

I would say that the electric flux through the loop is positive. This is because the electric flux is a measure of the electric field passing through a given area. In this case, the electric field lines are directed towards the loop, indicating a positive flux. The fact that the area vector is also pointing in the same direction as the electric field lines reinforces this idea.

However, it is important to note that the electric flux can also be negative or zero, depending on the situation. For example, if the point charge was negative, the electric field lines would be directed away from the loop and the flux would be negative. And if the loop was parallel to the electric field lines, the flux would be zero because no field lines are passing through the loop.

It is also important to mention that the concept of electric flux is often used in the context of enclosed surfaces, as you mentioned. In this case, the flux is calculated by taking the dot product of the electric field and the normal vector to the surface. This can result in a positive or negative value, depending on the direction of the electric field and the orientation of the surface.

In summary, the electric flux through the loop in this scenario is positive due to the direction of the electric field lines and the area vector. However, it is important to consider different scenarios and understand how the direction of the electric field and the orientation of the surface can affect the value of electric flux.