Electric Field and Force between two plates [homework question]

That blank attempt at the solution is somewhat bothersome. What's the voltage across the gap between the plates in either case?

 

Well I should really treat this like a homework problem. So the question becomes, in case a (nongrounded) lets say it's -3 and +3V. Is the second case 0 and +3 or 0 and +6?

 

Np, this is physics forum not art forum. If you look at your relevent equations, and then look at your picture, you have a voltage and a distance; you're looking for the electric field. You have the equation you need, with one (reasonable) assumption. First off, 2m is pretty large for a gap in capacitors, but it doesn't really matter, as long as we can assume that the length of the plates are long with respect to the gap, the field will be approximately uniform throughout the region between the plates. Then it's a matter of applying coloumbs law once you find the field. This will give you the force on the electron.

With our assumption, it doesn't matter if the electron was mid point, quarter way or pi/32 of the way through, the force would be (for all intensive purposes) the same.

 

Essentially, yes. If you want to find out for sure. Assume uniform charge density on either plate, the integrate the field contribution from each dL along the length of the plate for some arbitrary point (x,y) (you only need to do this in 2d to meet your picture). If you do that for both plates, then apply superposition and sum the contributions from both plates for all points (x,y) you will see that all points are approximately the same, especially far from the edges.

 

Yea, zero potential doesn't really mean anything. It's kind of like me saying that a block sitting on a table has 0 GPE or me saying that it has GPE mg(height of the table from the floor). Very analagous.