Why is charge a derived quantity

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Charge is considered a derived quantity because it is defined in relation to the fundamental unit of electric current, the ampere. The coulomb, the unit of electric charge, is expressed as ampere-seconds, highlighting its dependence on current. This derivation is practical, as measuring current through the force between wires is more straightforward than establishing a precise standard for charge. The discussion emphasizes the importance of the seven base units in the International System of Units (SI), from which all other units, including charge, are derived. Understanding this relationship helps clarify the foundational structure of measurement in physics.
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Why is charge a derived quantity?
 
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convention. Current was measured before charge.
 


There are seven base units from which all other units are derived.


-meter (length)
-kilogram (mass)
-second (time)
-ampere (electric current)
-kelvin (temperature)
-candela (luminous intensity)
-mole (concentration of substance)
​

Electric charge is measured in Coulombs, or Amperes seconds.
 
Last edited:
In SI, current is a fundamental unit (ampere) and charge is a derived unit (coulomb = ampere · second) for practical reasons. It's easier to implement the standard for current precisely, by measuring the force between two current-carrying wires, than it would be to implement a standard for charge precisely, involving something like measuring the force between two charges, or counting electrons.
 


AbsoluteZer0 said:
Electric charge is measured in Coulombs, or Amperes per second.
Ampere seconds, not amperes per second.
 


AlephZero said:
Ampere seconds, not amperes per second.

My apologies.
Edited and corrected.
 
No prob. Thanks for that. Really cleared it up
 

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