In a Millikan oil-drop experiment, the charges on several different oil drops were as follows: −5.92; −4.44; −2.96; −8.88. The units are arbitrary. What is the likely value of the electronic charge in these arbitrary units?
A)−1.11
B)−1.48
C)−2.22
D)−2.96
E)−5.55

Question

Quizplus · Accepted Answer

The electronic charge (magnitude) is given by the equation:
|e| = (mg)/(qd)
where g is the acceleration due to gravity, m is the mass of the oil drop, q is its charge, and d is the viscosity. Since we are working in arbitrary units, we can assume that g, m, and d are all equal to 1. Therefore, we have:
|e| = 1/q
Taking the reciprocals of the charges given, we get:
-0.169, -0.225, -0.338, and -0.112
The average of these values is approximately -0.211. Taking the reciprocal of this average gives us:
-1.48, which is closest to choice B.

In a Millikan Oil-Drop Experiment, the Charges on Several Different