An Improved Method of Measuring Charge Using a Simple Device

Charge measurement has many potential applications in research involving charged particles and other fields. Established methods, such as the valve electrometer and the solid-state electrometer, guarantee accuracy but are costly and relatively inconvenient. Thus, accurately measuring charge in common experimental settings is very challenging. This paper proposes an alternative method of charge measurement, which is lower in cost while maintaining assured accuracy. The proposed device consists of a metal ball suspended on a non-conducting string between two charged metal plates. An electrostatic generator is used to charge the metal ball and the plates. Using the derived relationship between charge and deflection, the charge on the ball can be detected by measuring the deflection distance. After optimizing the parameters of the device theoretically using the genetics algorithm, the measurement accuracy can be improved. In the experiment, the accuracy of the device is validated, and using the optimized parameters, the limit of the device’s measurement is found to be between 1.88×10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−10</sup>C and 1.98×10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">–10</sup>C.