Why do so many answers give wrong definitions of ampere?

Answer 1

Probably because not very many people have a good understanding of the meaning of that word. If you understand it, feel free to go and correct the definitions.

AnswerLet's start by giving the correct definition of the ampere, which is an SI Base Unit and uses the magnetic effect of an electric current to provide its definition: "The ampere (symbol: A) is defined as 'that constant current which, when maintained in two straight parallel conductors of infinite length and of negligible circular cross-sectional area, and placed one metre apart in a vacuum, would produce between them a force equal to 2×10-7newton per metre of length".

Unfortunately, many textbooks define the ampere as a "coulomb per second". Although the ampere is certainly equivalent to a "coulomb per second", it is not defined in that way or in terms of the coulomb or the second.

This incorrect definition is probably also perpetuated by high school teachers who, while having qualifications in education, do not have qualifications in science or in electrical engineering.

As a matter of interest, the definition of the ampere is likely to change from its present form in the not-too-distant future, as the each of the SI Base Units are being reviewed and, down the road, it might well be defined in terms of the fundamental unit of charge (i.e. the charge on a single electron, not the coulomb) and of time. But not yet!