Imperial and US customary measurement systems (42 US gallons, 34.97 imperial gallons or 159.0 litres) used in the oil industry has the dimension of volume and could be replaced by the gallon, cubic metre or litre. The definitions of potential difference (volt), electric current (ampere), electrical resistance (ohm) were defined in terms of metric units, international agreement having been reached at a series of IEC Congress in Chicago between 1881 and 1906 when the electrical industry was in its infancy. At that time the metric system had become established in continental Europe while in the United Kingdom metrication was an active issue. Similarly, the units of
History of electrochemistry Weber defined the absolute unit of electrical resistance (which was named the ohm after Georg Ohm). Weber's name is now used as a unit name to describe magnetic flux, the weber. German physicist Johann Hittorf concluded that "ion movement" caused electric current. In 1853 Hittorf noticed that some ions traveled more rapidly than others. This observation led to the concept of transport number, the rate at which particular ions carried the electric current. Hittorf measured the changes in the concentration of electrolysed solutions, computed from these the transport numbers (relative carrying capacities) of many ions, and, in 1869, published his