The elementary charge (symbol e or sometimes q) is the electric charge carried by a single proton, or equivalently, the negative of the electric charge carried by a single electron. This is a fundamental physical constant and the unit of electric charge in the system of atomic units as well as some other systems of natural units. It has a value of 1.602 176 487 × 10-19 C, according to the 2006 CODATA list of physical constants[1]. In the centimetre gram second system of units, the value is 4.803 204 273 × 10-10 statcoulombs. Since it was first measured in Robert Millikan's famous oil-drop experiment in 1909, the elementary charge has been considered indivisible. Quarks, first posited in the 1960s, have fractional electric charges (in units of e/3 and 2e/3) so that now the term elementary charge referring to the charge on an electron is no longer strictly correct. In 1982 Robert Laughlin tried to explain the fractional quantum Hall effect by predicting the existence of fractionally charged quasiparticles. In 1995, the fractional charge of Laughlin quasiparticles was measured directly in a quantum antidot electrometer at Stony Brook University, New York. In 1997, two groups of physicists at the Weizmann Institute of Science in Rehovot, Israel, and at the Commissariat à l'énergie atomique laboratory near Paris, claimed to have detected such quasiparticles carrying an electric current.
External links
- "Measurement of fractional charge" (Science Report) 1995
- "Quantum antidot electrometer"
- "Fractional charge carriers discovered" - Physics Web article 1997-10-24
- "Direct observation of a fractional charge" (letter to Nature) 1997
References
Fundamentals of Physics, 7th Ed., Halliday, Robert Resnick, and Jearl Walker. Wiley, 2005
