The Electric Potential Equation

[meaghan]

Homework Statement

An object with charge q = −4.00×10−9 C is placed in a region of uniform electric field and is released from rest at point A. After the charge has moved to point B, 0.500 m to the right, it has kinetic energy 5.00×10−7 J .What is the magnitude of the electric field?

Homework Equations

U = kQ/r^2
F = Eq
W = Fd
U = Eqd

The Attempt at a Solution

I was thinking that I could maybe set the voltage difference equal to the electric field * charge * distance since the part before asked that if the electric potential at point A is +30.0 V, what is the electric potential at point B? Which the answer was 155 V.

 

[haruspex]

I was thinking that I could maybe set the voltage difference equal to the electric field * charge * distance since the part before asked that if the electric potential at point A is +30.0 V, what is the electric potential at point B? Which the answer was 155 V.

By what logic, theory, or standard equation is a potential equal to field x charge x distance?