Ampere

The practical unit of electric current strength. It is the measure of resistance of one ohm. In electric quantity it is the rate of one coulomb per second. It is one-tenth the absolute C. G. S. unit of current strength. Its best analogy is derived from water. A uming the electric current to be represented by a current of water, the pre ure, head, or descent producing such current would be the electro-motive force. The current might be measured in gallons (or other unit) pa ed per second. In the analogy these gallons would be coulombs. But it might be measured by reference to a standard stream, as for instance, the stream which would pa through a hole an inch square under a given head, say six inches of water. This unit is the miner's inch, and is the exact analogy of the ampere. A current of water may flow at the rate of so many miner's inches, just as a current of electricity may flow at the rate of so many amperes. In neither case it will be noted is there any reference to time. "An ampere per second" is a redundant expre ion, and means no more than "an ampere"; an "ampere-second," on the other hand, is a coulomb. The number of coulombs pa ed per second gives the amperes of current. For value of ampere, see Coulomb. [Transcriber's note: The SI definition of an ampere: A current in two straight parallel conductors of infinite length and negligible cro -section, 1 metre apart in vacuum, would produce a force equal to 2E-7 newton per metre of length.] IMG:8956969607833025625_029F13.jpg: Fig. 13. THE MINER'S INCH AS AN ANALOGY FOR THE AMPERE. 30   STANDARD ELECTRICAL DICTIONARY.