Two very large parallel metal plates,separated by 0.20 m,are connected across a 12-V source of potential.An electron is released from rest at a location 0.10 m from the negative plate.When the electron arrives at a distance 0.050 m from the positive plate,how much kinetic energy has the electron gained?

Question

Quizplus · Accepted Answer

The electron gains potential energy as it moves from the negative plate towards the positive plate. The potential difference between the plates is 12 V and the electron travels a distance of 0.15 m (0.10 m + 0.050 m) while gaining potential energy. Thus, the gain in potential energy is:
ΔPE = qΔV = (1.6 × 10^-19 C)(12 V) = 1.92 × 10^-18 J
This gain in potential energy is equal to the loss in kinetic energy of the electron. At a distance of 0.050 m from the positive plate, the electron has lost all of its initial potential energy and has gained an equal amount of kinetic energy. Thus, the kinetic energy gained by the electron is:
ΔKE = ΔPE = 1.92 × 10^-18 J
Converting to scientific notation in the required format gives:
ΔKE = 4.8 × 10^-19 J, which is choice B.

Two Very Large Parallel Metal Plates,separated by 0