The Ohm is a unit for electrical resistance derived from the System of Units( SI). It is named after the German physicist Georg Simon Ohm (1787 to 1854) and is indicated with the capital Greek letter ` Omega`.
According to the derivation in the system of units, 1 Ohm represents the ratio between 1 volt (V) to 1 ampere (A): 1 Ohm = 1 V/1 A. The relationship between voltage, current and resistance is also specified in Ohm's law. In addition, the ohm is defined in the electrostatic and electromagnetic CGS (centimeter, gram, second) systems in second/centimeter and centimeter/second, respectively.
The ohm forms the basic unit and is specified with prefixes as milli-ohm (`10^-3`), micro-ohm (`10^-6`), kilo-ohm (`10^3`), mega-ohm (`10^6`), giga-ohm (`10^9`), and tera-ohm (`10^12`).