Hawkins Electrical Guide v. 01 (of 10) / Questions, Answers, & Illustrations, A progressive course of study for engineers, electricians, students and those desiring to acquire a working knowledge of electricity and its applications

by N. Hawkins

Ans. A volt is that electromotive force (E. M. F.) which produces a current of one ampere against a resistance of one ohm.

Ques. What is an ampere?

Ans. An ampere is the current produced by an E. M. F. of one volt in a circuit having a resistance of one ohm. It is that quantity of electricity which will deposit .005084 grain of copper per second.

Ques. What is an ohm?

Ans. 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 mass, of a constant cross sectional area, and of the length of 106.3 centimeters.

Ohm’s Law.—In a given circuit, the amount of current in amperes is equal to the E. M. F. in volts divided by the resistance in ohms; that is:

current = pressure / resistance = volts / ohms

expressed as a formula:

I = E/R (1)

in which