Why isn't CHARGE a fundamental quantity rather than CURRENT?

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SUMMARY

The discussion centers on the classification of electric current and charge within the SI unit system, specifically questioning why "electric current" is designated as a fundamental quantity while "charge" is not. Participants argue that the ampere, defined as one coulomb per second, appears more like a derived unit, suggesting that the coulomb should be recognized as the fundamental unit. The conversation highlights the experimental challenges in defining these units and the subjective nature of what constitutes a fundamental quantity in physics.

PREREQUISITES
  • Understanding of SI units and their classifications
  • Basic knowledge of electric current and charge
  • Familiarity with the definitions of ampere and coulomb
  • Concepts of experimental measurement and accuracy in physics
NEXT STEPS
  • Research the historical context of SI unit definitions and changes
  • Explore the experimental methods used to define the ampere
  • Investigate alternative definitions for the coulomb and their implications
  • Learn about the role of fundamental quantities in physics and their classifications
USEFUL FOR

Physicists, electrical engineers, and students studying electromagnetism who seek a deeper understanding of the definitions and classifications of electric units within the SI system.

tan99
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Almost all physics or engineering textbooks have a table of the SI units
that are based on six fundamental quantities. The one that is listed for
the quantity "electric current" is always "ampere". However, usually a few
pages past this fundamental table lies a definition of the ampere. 1 ampere
= 1 coulomb/second. This makes it sound more like a derived unit than a
fundamental unit. It seems more likely that the fundamental quantity
"electric current" should be replaced by the quantity "charge" and that the
fundamental unit should be the coulomb. While amperes can be broken down
into coulombs and seconds, the coulomb cannot be broken down (except to a
specific count of electrons or protons). Why does there seem to be some
contradiction between the definition of a fundamental quantity (a quantity
that can't be described in terms of another quantity) and the definition of
electric current? Why isn't charge along with the coulomb included in the
fundamental quantities table?
 
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tan99 said:
Almost all physics or engineering textbooks have a table of the SI units
that are based on six fundamental quantities. The one that is listed for
the quantity "electric current" is always "ampere". However, usually a few
pages past this fundamental table lies a definition of the ampere. 1 ampere
= 1 coulomb/second. This makes it sound more like a derived unit than a
fundamental unit. It seems more likely that the fundamental quantity
"electric current" should be replaced by the quantity "charge" and that the
fundamental unit should be the coulomb. While amperes can be broken down
into coulombs and seconds, the coulomb cannot be broken down (except to a
specific count of electrons or protons). Why does there seem to be some
contradiction between the definition of a fundamental quantity (a quantity
that can't be described in terms of another quantity) and the definition of
electric current? Why isn't charge along with the coulomb included in the
fundamental quantities table?

It's true that 1 amp=1 Coulomb/second but of course 1 Coulomb=1 Amp second.I think the choice of what's considered to be more fundamental is guided largely by the experimental ease by which the unit can be established.The Ampere is defined with reference to the force between parallel current carrying wires which presents experimental difficulties to establish exactly but nevertheless is measurable to a high degree of accuracy.If we don't define the Coulomb with reference to the Ampere then how else should we define it?There must be ways but I'm assuming that the experiments needed to establish the unit are less accurate than the ones currently used.Anyway,like yourself I feel that the Coulomb is more fundamental than the Ampere.
 
I wouldn't read very much into the fact that Amperes are an SI base unit, rather than Coulombs.
Heck, moles are an SI base unit, and it's not even a measure of anything.
 

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