In recognition of his contribution to the creation of modern electrical science , an international convention , signed at the 1881 International Exposition of Electricity , established the ampere as a standard unit of electrical measurement , along with the coulomb , volt , ohm , and watt , which are named , respectively , after Ampère 's contemporaries Charles-Augustin de Coulomb of France , Alessandro Volta of Italy , Georg Ohm of Germany , and James Watt of Scotland .