A study of Bethenod´s phenomenon

In the light of a detailed experimental investigation, the status of the existing theory on Bethenod´s phenomenon is discussed. A critical review of the time-varying parameter (TVP) theory of Minorsky, revealing some important points strangely missed by researchers in the field so far, leads to the assertion that the phenomenon cannot be explained by such a theory. A plausible theory for Rethenod´s pendulum is developed here and is extended to the difficult case of the frequently encountered bell-shaped inductance profile, using the novel concept of a dynamically equivalent continuously activated pendulum (DECAP).