Since the exact measurement of resistance is slow, various types of ohmmeters have been invented to give direct readings in ohms.
The ohm is that resistance which causes a potential drop of one absolute volt when a steady current of one absolute ampere flows through it. The international ohm is based on a specified conductor. It is the resistance of a uniform thread of mercury in a capillary tube of such diameter that the thread is 106.3 cm. long, weighs 14.4521 grams, and has a temperature of 0 degrees Centigrade.
