Elementary charge

The elementary charge is the positive magnitude of the proton’s electric charge and the negative of the electron’s charge. It is the SI unit of electric charge, exactly 1.602176634 × 10⁻¹⁹ coulombs.

Electric charge: A fundamental property of matter that determines electromagnetic interactions. The elementary charge is the smallest charge magnitude carried by isolated particles.
Charge quantization: The observation that electric charge occurs in discrete amounts rather than arbitrary values. The elementary charge is the unit in which many particle charges are quantized.
Charles-Augustin de Coulomb: French physicist whose experiments established a quantitative law for electrostatic forces. His work helped make electric charge measurable as a physical quantity.
Ampere: The SI unit of electric current, defined by fixing the numerical value of the elementary charge. Its modern definition makes the elementary charge foundational to current measurement.
Proton: A positively charged subatomic particle found in atomic nuclei. A proton carries exactly one elementary charge.
Millikan oil-drop experiment: An experiment that measured the electron’s charge by observing charged oil droplets in an electric field. Its measurements revealed charge values clustered around a common smallest magnitude.
J. J. Thomson: British physicist who discovered the electron and measured its charge-to-mass ratio. Identifying the electron made its charge a central target of measurement.
Faraday constant: The electric charge per mole of elementary charges, approximately 96,485 coulombs per mole. It converts charge per particle into charge per mole for electrochemical calculations.
Electron: A negatively charged elementary particle found in atoms and many other systems. An electron carries exactly the negative of the elementary charge.
Fine-structure constant: A dimensionless constant that sets the strength of electromagnetic interactions. It relates the elementary charge to other constants and the electromagnetic coupling.

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