Cracking the SAT Physics Subject Test

This tells us that the potential of the positive plate is greater than the potential of the
negative plate, by the amount Ed.

The Skinny on

Potentials

Remember these

three key facts:

1. A positive charge
   moves from high
   potential to low
   potential.


2. A negative charge
   moves from low potential
   to high potential.


3. In either case, the
   electric potential energy
   decreases, as it is becoming
   kinetic energy.

Now that we know how to calculate electric potential, let’s revisit electric
potential energy. The applications of electric potential all follow from this one
fundamental equation:

Change in Electric Potential Energy

∆U = q∆Φ = qV

That is, the change in potential energy is given by the product of a charge q and the
potential difference between the two points it travels between, q∆Φ. This can also
can be expressed as qV, where V is defined as potential difference (or the change in
potential) and is known as voltage.