The ohm (symbol Ω ) is the unit derived from Electrical resistance of the international Système (IF). It was named in honor of Georg Ohm.

Definition: Electrical resistance between two points of a driver when a constant potential difference of 1 Volt, applied between these two points, produced in this driver a current of 1 amp the known as driver being the seat of no electromotive Force.

The ohm thus corresponds to V.A^-1 or in basic units: m.kg.s^-3.A^-2 .

One calls also Loi of Ohm the relation:

$U\; =\; R.I\; \backslash ,$ like $R\; =\; U/I\; \backslash ,$ and $I\; =\; U/R\; \backslash ,$

With $U\; \backslash ,$ in Volt, $I\; \backslash ,$ in Amp (unit) and $R\; \backslash ,$ in ohm.

See also: Ohmmeter