How Do Surface Charges Affect E-field Patterns in Prisms and Cubes?

[ch5112]

Please refer to the image that is attached

Homework Statement

For each of these prisms and cubes (a-f), state whether the surface encloses a:

-net positive charge
-net negative charge or
- a zero net charge

Homework Equations

The Attempt at a Solution

The E-field is everywhere parallel to the page, so there is no flux through the top and bottom surfaces, The E-field is uniform over each face of the surface in the direction shown. The field streang in N/C is also shown for each surface.

 

[Spinnor]

You might ask: Do the field lines end or begin in the shape in question, if so you have charge in the shape. If the field lines both end and begin in the shape in question the only way to have zero charge is if an equal number of lines enter and exit the shape.

What are your guesses?