I=nqvs .I Current intensity q in a conductor, charge quantity q of each charge, charge quantity n of each charge, number of free charges contained in unit volume n, cross-sectional area of S conductor, and direction moving rate of free charges in V conductor.

Scientifically, the amount of electricity passing through any section of a conductor in unit time is called current intensity, which is called current for short. Usually expressed by the letter I, its unit is ampere. André-Marie Ampère (1775- 1836), a French chemist, has made outstanding achievements in the research of electromagnetic action, and also made contributions in mathematics and physics.