What is the dimension of the electric charge

Elemental charge

The electrical charge cannot assume any numerical value, but only occurs in multiples of a very small minimum charge. The small number is calledElemental charge, symbolized with e and amounts to:

1 e = 1.60217733 × 10-19 C.

The C stands for the SI unit Coulomb the electric charge or 'amount of electricity' and was named after the French physicist Charles Augustin de Coulomb (1736-1806) named. In terms of dimensions, the electrical charge corresponds to the product of the current strength (SI unit:Amp) and time (SI unit: second).

The Millikan attempt

The numerical value for the elementary charge is very small. How do you know this microscopic value so precisely? In 1909, the American physicist led Robert Andrews Millikan (1868 - 1953) carried out a historical, physical experiment, the measuring principle of which is simple and ingenious: He made electrically charged oil droplets float in the electric field of a plate capacitor. From the Equilibrium condition 'Gravity (G = mg) is compensated by an electric field force (F = QE) 'and the knowledge of the electric field strengthE. (which is equal to the electrical voltage due to the distance between the plates of the capacitors), Millikan was able to determine the charge of the oil droplets Q shut down. When looking at many oil droplets, it becomes apparent that their charges are always a multiple of the elementary charge e be. Millikan received the Nobel Prize in Physics in 1923 for this excellent idea with brilliant results.


In physics it is very convenient to calculate the electrical charge of the particles in units of the elementary charge e to express. There are both positive and negativeMultiples possible. Electrically neutral particles have zero times the elementary charge. The following electrical charges apply, among others:

  • Proton: 1 e
  • Electron: -1 e
  • Positron: +1 e
  • Neutrons: 0

exceptions prove the rule

However, particle physics also knows a few exotic ones, the not an integral multiple of e are. Quarks (the building blocks of hadrons) and X bosons as well as Y bosons (hypothetical particles from the GUT era) third-number charges.