Why electric current is a SI base unit?

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SUMMARY

The electric current is defined as a base unit in the International System of Units (SI) due to its realizability and portability, as opposed to the coulomb, which measures charge. Current induces measurable forces in conductors, making it a practical choice for a base unit. Future definitions will establish the ampere based on a specific flow of elementary charges, reinforcing its status as the base unit. Bureaucratic decisions play a significant role in maintaining this classification.

PREREQUISITES
  • Understanding of SI base units
  • Knowledge of electrical concepts such as current and charge
  • Familiarity with the definition of the ampere
  • Awareness of the proposed changes to SI units regarding elementary charge
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  • Research the definition and implications of the ampere in the SI system
  • Explore the concept of elementary charge and its significance in physics
  • Learn about the historical context of SI unit definitions
  • Investigate the impact of bureaucratic decisions on scientific standards
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Physicists, electrical engineers, educators, and anyone interested in the foundations of measurement in science.

wasi-uz-zaman
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hi, why electric current is a SI base unit - why not couloumb?
 
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Wikipedia explains it quite well.
 
wasi-uz-zaman said:
hi, why electric current is a SI base unit - why not couloumb?
In the past, realizability. A system of units needs to have base units that are realizable and portable. How do you measure charge? A flowing current induces a force on the wires through which the current is flowing. That force is measurable (but there are better realizations).

In the future, it's a bit fuzzier. The proposed change to the International System makes the elementary charge (the charge of one electron) a defined constant, exactly 1/(6.2415093×1018) coulombs (or something to that effect). The ampere will be defined in terms of a current that has specific number of elementary charges flowing past a point per second. So which is the base unit now, the ampere or the coulomb? It's still the ampere. The reason: Because they said so. Bureaucratic inertia is an incredibly powerful force, even though it cannot be expressed in Newtons.
 

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