Metrication in the United States There are no U.S. customary units for electric current, potential difference, or charge since these concepts were developed after the international adoption of metric in science. The metric units ampere, volt, ohm and coulomb are the only units used. The SI term hertz has replaced the term "cycles per second" as a unit of frequency. Energy is often measured in watt hours, BTUs, therms or calories rather than the SI joule. Residential and commercial electrical energy use is metered and billed in kilowatt hours, kW·h, as in most metric countries. Force measurements regularly use the pound instead of the SI
Martin Ohm 1852; and he also taught in the military school from 1826 to 1849. Ohm was the first to fully develop the theory of the exponential "a" when both "a" and "b" are complex numbers in 1823. He is also often credited with introducing the name "golden section" ("goldener Schnitt"). Ohm's students included Friedrich August, Friedrich Bachmann, Elwin Bruno Christoffel, Paul Bachmann, Joseph Brutkowski, Heinrich Eduard Heine, Rudolf Lipschitz, Leo Pochhammer, Friedrich Prym, Wilhelm Wagner, Hermann Waldaestel, Wilhelm Wernicke, Elena Gerz, Valentien Gerz, and Johanna Gerz. Martin Ohm Martin Ohm (May 6, 1792, Erlangen – April 1, 1872, Berlin) was a