Physical Science, Measurement and Instrumentation, Management and Education, IEE Proceedings A

When free charge exists in a conducting medium, the rate at which charge relaxes or decays is determined by the conductivity and the permittivity of the medium in which free charge is initially placed. The relaxation time is defined for this rate of charge decay. It is commonly believed that, when the conductivity of the medium is constant, the relaxation time is independent of the size and shape of the container in which the charged medium is enclosed. The author has re-examined the theory of charge relaxation, starting from fundamental equations for the case where the charged liquid is partly filled, and has come to a different conclusion from that which is commonly understood. The result shows that, when an open surface of the charged medium exists within a conducting container, the relaxation time is a function of the shape. However, the highest value of the ratio of a new relaxation time to a conventional relaxation time is two, regardless of the difference of permittivities in the two media.