The diagram below shows a particle with positive charge q accelerating between two conducting plates at potentials \({V_1}\) and \({V_2}\).

Which of the following is the kinetic energy gained by the charge in moving between the plates?

A.     \({V_2}q\)

B.     \({V_1}q\)

C.     \(({V_1} - {V_2})q\)

D.     \(({V_2} - {V_1})q\)

C

The vast majority of students incorrectly chose D as their answer. Kinetic energy gained is equal to potential energy lost. Furthermore, kinetic energy can only be positive, so, whether \(q\) is negative or positive, the only correct response can be C.