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Johnson–Nyquist noise (thermal noise, Johnson noise, or Nyquist noise) is the electronic noise generated by the thermal agitation of the charge carriers (usually the electrons) inside an electrical conductor at equilibrium, which happens regardless of any applied voltage.
Static electricity is an imbalance of electric charges within or on the surface of a material. The charge remains until it can move away by an electric current or electrical discharge . The word "static" is used to differentiate it from current electricity , where an electric charge flows through an electrical conductor .
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Different types of noise are generated by different devices and different processes. Thermal noise is unavoidable at non-zero temperature (see fluctuation-dissipation theorem), while other types depend mostly on device type (such as shot noise, [1] [3] which needs a steep potential barrier) or manufacturing quality and semiconductor defects, such as conductance fluctuations, including 1/f noise.
Common-mode coupling: noise appears in phase (in the same direction) on two conductors. Differential-mode coupling: noise appears out of phase (in opposite directions) on two conductors. Inductive coupling occurs where the source and victim are separated by a short distance (typically less than a wavelength ).
Aeroacoustics is the study of noise generated by air movement, for instance via turbulence, and the movement of sound through the fluid air. This knowledge was applied in the 1920s and '30s to detect aircraft before radar was invented and is applied in acoustical engineering to study how to quieten aircraft .
The torsional deflection of a simple cylinder cannot radiate efficiently acoustic noise, but with particular boundary conditions the stator can radiate acoustic noise under torque ripple excitation. [8] Structure-borne noise can also be generated by torque ripple when rotor shaft line vibrations propagate to the frame [9] and shaft line.
Speculations of Jean-Antoine Nollet had led to the issue of the electrical nature of lightning being posed as a prize question at Bordeaux in 1749. In 1750, it was the subject of public discussion in France with a dissertation of Denis Barberet receiving a prize in Bordeaux. Barberet proposed a cause in line with the triboelectric effect.