the standard unit in the measure of electrical resistance, being the resistance of a circuit in which a potential difference of one volt produces a current of one ampere. as defined by the international electrical congress in 1893, and by united states statute, it is a resistance substantially equal to 109 units of resistance of the c.g.s. system of electro-magnetic units, and is represented by the resistance offered to an unvarying electric current by a column of mercury at the temperature of melting ice 14.4521 grams in mass, of a constant cross-sectional area, and of the length of 106.3 centimeters. as thus defined it is called the international ohm.