Calculation of the Fundamental Electric Charge with a Millikan Oil Drop Apparatus

Noah Fuge D'Antonio, New Mexico Institute of Mining and Technology


Using a Millikan oil drop apparatus, information obtained from drops falling at terminal velocity and suspended between capacitor plates can be used to calculate the charge q on a oil drops. Using a large number of drops, we attempt to determine the value of the fundamental electric charge e that best fits the equation q e = n, where n is an integer. By attempting to minimize the square of the non-integer residual for all drops, the best fit value for e obtained was emeasured = (3.8 ± 0.4 ∗ 10−19) C. As the tabulated and defined value of etabulated ≈ 1.602 ∗ 10−19C is far outside the bounds of random error, there was likely significant systematic error with the experimental setup or issues with data analysis. Potential sources of experimental error contributing to this discrepancy are examined, and the drawbacks of using a simple residual minimization formula are discussed.