History Volt

alessandro volta

in 1800, result of professional disagreement on galvanic response advocated luigi galvani, alessandro volta developed so-called voltaic pile, forerunner of battery, produced steady electric current. volta had determined effective pair of dissimilar metals produce electricity zinc , silver. in 1861, latimer clark , sir charles bright coined name volt unit of resistance. 1873, british association advancement of science had defined volt, ohm, , farad. in 1881, international electrical congress, international electrotechnical commission (iec), approved volt unit electromotive force. made volt equal 10 cgs units of voltage, cgs system @ time being customary system of units in science. chose such ratio because cgs unit of voltage inconveniently small , 1 volt in definition approximately emf of daniell cell, standard source of voltage in telegraph systems of day. @ time, volt defined potential difference [i.e., nowadays called voltage (difference) ] across conductor when current of 1 ampere dissipates 1 watt of power.

group photograph of hermann helmholtz, wife (seated) , academic friends hugo kronecker (left), thomas corwin mendenhall (right), henry villard (center) during international electrical congress

the international volt defined in 1893 1/1.434 of emf of clark cell. definition abandoned in 1908 in favor of definition based on international ohm , international ampere until entire set of reproducible units abandoned in 1948.

prior development of josephson junction voltage standard, volt maintained in national laboratories using specially constructed batteries called standard cells . united states used design called weston cell 1905 1972.