Relation To Elementary Charge
The elementary charge, the charge of a proton (equivalently, the negative of the charge of an electron), is approximately 1.602176487(40)×10−19 C. In SI, the elementary charge in coulombs is an approximate value: no experiment can be infinitely accurate. However, in other unit systems, the elementary charge has an exact value by definition, and other charges are ultimately measured relative to the elementary charge. For example, in conventional electrical units, the values of the Josephson constant KJ and von Klitzing constant RK are exact defined values (written KJ-90 and RK-90), and it follows that the elementary charge is also an exact defined value in this unit system. Specifically, exactly. SI itself may someday change its definitions in a similar way. For example, one possible proposed redefinition is "the ampere...is such that the value of the elementary charge e (charge on a proton) is exactly 1.602176487×10−19 coulomb" This proposal is not yet accepted as part of the SI system: The SI definitions are unlikely to change until at least 2015.
Read more about this topic: Coulomb
Famous quotes containing the words relation to, relation, elementary and/or charge:
“Hesitation increases in relation to risk in equal proportion to age.”
—Ernest Hemingway (1899–1961)
“Only in a house where one has learnt to be lonely does one have this solicitude for things. One’s relation to them, the daily seeing or touching, begins to become love, and to lay one open to pain.”
—Elizabeth Bowen (1899–1973)
“As if paralyzed by the national fear of ideas, the democratic distrust of whatever strikes beneath the prevailing platitudes, it evades all resolute and honest dealing with what, after all, must be every healthy literature’s elementary materials.”
—H.L. (Henry Lewis)
“The Germans are called brutal, the Spanish cruel, the Americans superficial, and so on; but we are perfide Albion, the island of hypocrites, the people who have built up an Empire with a Bible in one hand, a pistol in the other, and financial concessions in both pockets. Is the charge true? I think it is.”
—E.M. (Edward Morgan)