An Etymological Dictionary of Astronomy and Astrophysics

The mean square noise voltage across a resistance in thermal equilibrium is four times the product of the resistance, Boltzmann’s constant, the absolute temperature, and the frequency range within which the voltage is measured. → Johnson-Nyquist noise.

See also: Named after Harry Nyquist (1889-1976), a Swedish-born American physicist, who made important contributions to information theory. → Johnson-Nyquist noise; → formula.