Chapter 20, Problem 16PCE

Predict/Explain An electron is released from rest in a region of space with a nonzero electric field. (a) As the electron moves, does the electric potential energy of the system increase, decrease, or stay the same? (b) Choose the best explanation from among the following:

1. I.                    Because the electron has a negative charge its electric potential energy doesn’t decrease, as one might expect, but increases instead.
2. II.                  As the electron begins to move, its kinetic energy increases. The increase in kinetic energy is equal to the decrease in the electric potential energy of the system.
3. III.               The electron will move perpendicular to the electric field, and hence its electric potential energy will remain the same.