Abstract
This conference talk serves two purposes. By considering a thought experiment involving two connected wires with different work functions, it shows that the "practical voltage" measured by a galvanometer-type voltmeter (or modern equivalents) does NOT coincide with the quantity "IEC voltage" defined in the International Standard for Electromagnetism and related documents. The probable cause of this discrepancy and some other related issues will be discussed. Further study of the thought experiment leads to a more complete explanation of patch fields, and insights into the theory of electron emission, and into the behavior of charged entities near metal surfaces that exhibit areas of different local work function.