I have two problems, both using different equations for electric potential. Confused on when to use which.
Two parallel plates connected by a battery whose electric potential is 12V. One plate Has charge density σ+ and the other has Charge density σ+. The plates are spaced 3x10-3m. We want to find the electric field. The way the problem is solved:
Combining the two above:
The next problem wants to know the electric potential energy of moving a proton like the attached picture.
It is solved like this:
Why I’m the first problem did we say ΔV=Ed
And in the second problem