@Carl Love 

Thanks again for your reply, I really appreciate you help.

The view option was indeed what I needed. Now, It all looks nice and good.

However, there is one mistake Maple makes: It draws all the "mountains" in the field in the positive z-direction even though one of them would have to be negative (since it is a negative charge). In the vector plot, this is correct, because the arrows point towards the negative charge. But somehow, Maple gets it wrong for the other plot. When I do not set the view-option, the "mountain" that would have to go into negative z-direction is somehow cut off and looks differnt from the others, so Maple does seem to realize there is something special about this one.

Picture: http://puu.sh/aoTSi/01e900536a.jpg

Worksheet: https://copy.com/TyYJAL7K2Dr2i7ar (is always updated to newest version)

@Carl Love 

Thank you very much for your answer, now it works. Finally, I would like to plot my results. However, the electric potential EAbs is very large at some points and nearly flat at others. That means that the plot is not nice because it just shows some very sharp spikes, nothning else.

What I would like to do is also determine the z-axis. Then, I could cut off some of the spikes and show more of the structure instead. Is that possible?

Thank you very much for your answer.

First, another question: What does the :- syntax (such as in VectorCalculus:-Norm) mean?

Secondly, I attached my file so you can have a look at it.

Worksheet: Coulomb_Multiple_Charges.mw