AP Physics C E and M

Question

An electron moves 0.10 m along the direction of an electric field of a magnitude of 3.0 N/C. What is the change in electric potential energy between the electron’s initial and final points?

Answer 1

The magnitude of the energy change is qEd, where q is the 1.6 x 10^-19C charge of an electron. The sign of the the potential energy can be determined by whether the electron is storing energy or turning energy into kinetic energy by going the right way in the field. Here, the electron is gaining potential energy because it is going in the direction of the field (an electron feels the opposite of a + charged particle). With the force of the field... go down in potential, against the force...up in potential.