The New International Encyclopædia/Ohm

OHM (named after Georg S. Ohm). The practical unit of electrical resistance. It is defined as being the electrical resistance offered to the passage of an unvarying electric current by a column of mercury, 106.3 cm. long, of uniform cross-section, having a mass of 14.4521 grams, the mercury being at the temperature of 0° C. (This would require a cross-section of 1.00003 square millimeters.) The ohm is substantially equal to 10⁹ C.G.S. electro-magnetic units of resistance. See Electrical Units; Resistance, Electrical.