Ohm

About: Ohm is a research topic. Over the lifetime, 829 publications have been published within this topic receiving 7682 citations. The topic is also known as: Ω.

Hot electrons in germanium and Ohm's law

Abstract: The data of E. J. Ryder on the mobility of electrons in electric fields up to 40,000 volts per cm are analyzed. The mobility decreases many fold due to the influence of scattering by optical modes and due to increases of electron energy. It is estimated that electron “temperatures” as high as 4000°K have been produced in specimens having temperatures of atomic vibration of 300° K. The critical drift velocity above which there are deviations from Ohm's law is about 2.6 × 106 cm/sec. This is three times higher than the elementary theory and on explanation in terms of complex energy surfaces is proposed.

The quantum Hall effect as an electrical resistance standard

Abstract: The quantum Hall effect (QHE) provides an invariant reference for resistance linked to natural constants It is used worldwide to maintain and compare the unit of resistance The reproducibility reached today is almost two orders of magnitude better than the uncertainty of the determination of the ohm in the international system of units SI In this article, mainly the aspects of the QHE relevant for its metrological application are reviewed After a short introduction of the theoretical models describing the integer QHE, the properties of the devices used in metrology and the measurement techniques are described A detailed summary is given on the measurements carried out to demonstrate the universality of the quantized Hall resistance and to assess all the effects leading to deviations of the Hall resistance from the quantized value In addition, the present and future role of the QHE in the SI and the field of natural constants is discussed

Ohm's law for mean magnetic fields

Abstract: The magnetic fields associated with plasmas frequently exhibit small-amplitude MHD fluctuations. It is useful to have equations for the magnetic field averaged over these fluctuations, the so-called mean field equations. Under very general assumptions, it is shown that the effect of MHD fluctuations on a force-free plasma can be represented by one parameter in Ohm's law, which is effectively the coefficient of electric current viscosity.

Pulse sampling battery fuel gauging and resistance metering method and means

Abstract: A continuously operating low dissipation system for sensing the electrical resistance of an element while the element carries a normal operating current. A pulse of electrical energy having a regulated ohm's law related first parameter is switched through the element while a second ohm's law related parameter of the element's response to the energy pulse is simultaneously measured. These two known parameters provide the information necessary to determine the element's resistance using Ohm's law. In the preferred embodiment voltage and current are used as the two parameters. The system is calibrated for the regulated level of the first parameter while the second parameter is amplified and stored in a sampling circuit for continuous display between pulses as an indication of resistance. The pulse techniques of this disclosure allow continuous operation of the system without heating of the resistive element or excessive power use. The resistance indication is additionally useful for indicating the remaining charge in a battery where the indicated resistance is the battery's internal resistance. A distinct battery terminal voltage indication is also given.