Harry Nyquist was an electrical engineer whose work connected communication engineering with physical and mathematical limits. His 1928 theory explained thermal electrical fluctuations using thermodynamics and statistical mechanics, agreeing with John Bertrand Johnson's measurements.[ref]
In the classical regime , an approximately constant electrical resistance at temperature produces an open-circuit voltage expected value square over a one-sided frequency band of width . Here is the Boltzmann constant. The formula connects Johnson-Nyquist noise with both the physical conductor and the signal bandwidth through which it is observed.[ref]
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Harry Nyquist (1889-1976) was a notable engineer and physicist whose work significantly influenced the fields of communication theory, control systems, and signal processing. He is best known for the Nyquist theorem, which addresses the sampling of signals and is foundational in the field of digital communications. The Nyquist theorem states that to accurately reconstruct a continuous signal without loss of information, it must be sampled at least at twice the highest frequency present in the signal.