If I would displace a negative one-coulomb charge r meters from a positive charge, Q, the negative charge would gain electric potential energy that would be calculated by summing up all the values of the electric potentials along the line of its displacement, r. (I don't know calculus, but I have heard of integration.) Why then is the formula for electric potential KQ/r? Doesn't this come from multiplying the electric force at displacement r from Q with r? Why do we do that when the electric force is actually changing along the path of displacement and not constant? Is not this, for example, like multiplying the final acceleration of an object by the duration of the acceleration to find the final velocity, which is invalid because the acceleration is actually constantly changing along the path?