Coulomb Balance

This experiment used a Coulomb balance to determine how the Coulomb force is dependent on the charge of two objects and the distance between these charges. In the first part of the experiment, the charges on the conductive spheres were kept constant, while the distance was varied. The angle at which the suspended sphere returned to its original position was recorded ten times for eight different distances. The logarithm of this angle was graphed with respect to the logarithm of the distance. The resulting fit had a slope of -2.053±0.003, an error of 3% from the expected -2. The second part of the experiment kept the distance and one sphere’s applied voltage constant, while varying the voltage for the other sphere. The same angle was recorded for four different voltages. The logarithm of this angle was then plotted against the logarithm of the voltage. The linear fit produced a slope of 1.023±0.006, an error of 2% from the expected slope of 1. These results indicate that Coulomb’s Law is accurate.