Johnson-Nyquist noise

Johnson-Nyquist noise (sometimes only "Nyquist noise") is the equilibrium fluctuations of the electric current inside an electrical conductor, which happen without any applied voltage, due to the random thermal motion of the charge carriers (the electrons).

It is to be distinguished from Shot noise, which describes the additional current fluctuations that occur when a voltage is applied and a macroscopic current starts to flow.

The strength of Nyquist noise is related to the temperature and the resistance of the conductor.

See: Harry Nyquist, J. Johnson

• J. Johnson, "Thermal Agitation of Electricity in Conductors", Phys. Rev. 32, 97 (1928) -- the experiment
• H. Nyquist, "Thermal Agitation of Electric Charge in Conductors", Phys. Rev. 32, 110 (1928) -- the theory