# Why does electric field remain constant in parallel plates when distance changes?

Given the formula E0 = ∆V/d, why does electric field stay constant when distance changes?

If a property of parallel plates is that ∆V is constant, shouldn't E0 change as d changes?

• Where did you get your "property of parallel plates" from? Commented Jun 5, 2014 at 11:32
• My teacher. :P So I'm assuming ∆V decreases as distance decreases? Commented Jun 5, 2014 at 14:54
• If you keep the plates connected through a battery $|Delta V$ will be constant. If you isolate them, then Q will be constant. With constant Q comes constant E field - but if potential difference is constant the field must be a function of spacing. Commented Jun 5, 2014 at 20:08

"A property of parallel plates is that $\Delta V$ is constant."

That can only be true if Q changes. For constant Q the field for infinite plates will be constant but V will change ( you are doing work to pull the plates apart). If you maintain constant potential difference then the charge must change.

• I think that you are right and I was wrong.
– rob
Commented Jun 5, 2014 at 7:06