Ohm

—The practical unit of electrical resistance, equal to 10° C. G. S, electromagnetic units. It is named for G. S. Ohm, the German scientist. An ohm is equal to the resistance offered to an unvarying electric current by a column of mercury at 32° Fahr.. 14.4521 grams in ma , of a constant cro sectional area, and of the length of 106.3 centimeters. The value of the ohm, determined by a committee of the British A ociation in 1863, called the B. A. unit, was the resistance of a certain piece of copper wire. The so called legal ohm as adopted_at the International Congre of Electricians in Paris in 1884, was a correction of the B. A. unit and was defined as the resistance of a column of mercury one square millimeter in section and_106 centimeters long, at a temperature of 32° Fahr.