We have two conducting plates. One is moveable, the other is not moveable. The moveable has the charge of +1V. While the other plate has the charge 0V and is part of a enclosing envelopment. See fig:
But when we move the upper plate horizontaly shown in the figure below the capacitance gets lower.
In the figure the E-field and potential is plotted. How am I to motivate why the capacitance gets lower?
From the relevant equations we got:
The Attempt at a Solution
I tried to motivate that the E-field gets weaker because the distance is greater in the horizontal axis. Then i suppose that the value of V gets smaller when you calculate the potential between the metal plates by equation (2).
But this doesn't seem quite correct to me since the capacitance C is independent of V and Q. We see by equation 3 that the capacitance is dependent of the surface area S and the distance d.
But the surface is the same, the only thing that changes is the distance. But the vertical distance is still the same.
So how do i motivate that the value of the capacitance decreaces?