On the theory of electrical fluctuations

In a recent paper under this title Fürth (1948) has discussed the derivation and interpretation of Nyquist’s formula (Nyquist 1928), and presented a theory proposing to treat the fluctuations of electric current in a thermionic valve under all conditions of operation on a basis of thermodynamic equilibrium. The writer would like here to offer certain objections of a fundamental character to the latter undertaking and to make some suggestions of relevance to the problem. Fürth, in the first part of his paper, has provided an interesting alternative derivation of Nyquist’s theorem. He has there replaced the arbitrary network under consideration by an ensemble of N damped oscillatory circuits; the approximation to the given network may then be made as close as one pleases by choosing N sufficiently great.