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Topic Review
Electrochemistry
Electrochemistry is the branch of physical chemistry concerned with the relationship between electrical potential difference, as a measurable and quantitative phenomenon, and identifiable chemical change, with the potential difference as an outcome of a particular chemical change, or vice versa. These reactions involve electrons moving via an electronically-conducting phase (typically an external electrical circuit, but not necessarily, as in electroless plating) between electrodes separated by an ionically conducting and electronically insulating electrolyte (or ionic species in a solution). When a chemical reaction is driven by an electrical potential difference, as in electrolysis, or if a potential difference results from a chemical reaction as in a battery or fuel cell, it is called an electrochemical reaction. Unlike in other chemical reactions, in electrochemical reactions electrons are not transferred directly between atoms, ions, or molecules, but via the aforementioned electronically-conducting circuit. This phenomenon is what distinguishes an electrochemical reaction from a conventional chemical reaction.
  • 564
  • 14 Oct 2022
Topic Review
Electromagnetically Excited Acoustic Noise and Vibration
Electromagnetically excited acoustic noise is audible sound directly produced by materials vibrating under the excitation of electromagnetic forces. Some examples of electromagnetically excited acoustic noise include the hum of transformers, the whine of some rotating electric machines, or the buzz of fluorescent lamps. The hissing of high voltage transmission lines is due to corona discharge, not magnetism. The phenomenon is also called audible magnetic noise, electromagnetic acoustic noise, or electromagnetically-induced acoustic noise, or more rarely, electrical noise, "coil noise", or "coil whine", depending on the application. The term electromagnetic noise is generally avoided as the term is used in the field of electromagnetic compatibility, dealing with radio frequencies. The term electrical noise describes electrical perturbations occurring in electronic circuits, not sound. For the latter use, the terms electromagnetic vibrations or magnetic vibrations, focusing on the structural phenomenon are less ambiguous. Acoustic noise and vibrations due to electromagnetic forces can be seen as the reciprocal of microphonics, which describes how a mechanical vibration or acoustic noise can induce an undesired electrical perturbation.
  • 1.3K
  • 28 Oct 2022
Topic Review
Electron Cloud Densitometry
Electron cloud densitometry is an interdisciplinary technology that uses the principles of quantum mechanics by the electron beam shifting effect. The effect is that the electron beam passing through the electron cloud, in accordance with the general principle of superposition of the system, changes its intensity in proportion to the probability density of the electron cloud. It gives direct visualization of the individual shapes of atoms, molecules and chemical bonds.
  • 819
  • 18 Nov 2022
Topic Review
Electron Elastic-Collisions with Multi-Electron Atoms and Fullerene Molecules
The Regge pole-calculated low-energy electron elastic total cross sections (TCSs) of complex heavy multi-electron systems are characterized generally by dramatically sharp resonances manifesting negative-ion formation. These TCSs yield directly the anionic binding energies (BEs), the shape resonances (SRs) and the Ramsauer–Townsend(R-T) minima. From the TCSs unambiguous and reliable ground, metastable and excited states negative-ion BEs of the formed anions during the collisions are extracted and compared with the measured and/or calculated electron affinities (EAs) of the atoms and fullerene molecules. The novelty and generality of the Regge pole approach is in the extraction of rigorous negative-ion BEs from the TCSs, without any assistance whatsoever from either experiment or any other theory. The EA provides a stringent test of theoretical calculations when their results are compared with those from reliable measurements. For ground states collisions, the Regge pole-calculated negative ion BEs correspond to the challenging to calculate theoretically EAs, yielding outstanding agreement with the standard measured EAs for Au, Pt and the highly radioactive At atoms as well as for the C60 and C70 fullerenes.
  • 382
  • 12 Aug 2022
Topic Review
Electron Rest Mass
The electron rest mass (symbol: me) is the mass of a stationary electron, also known as the invariant mass of the electron. It is one of the fundamental constants of physics. It has a value of about 9.109×10−31 kilograms or about 5.486×10−4 daltons, equivalent to an energy of about 8.187×10−14 joules or about 0.5110 MeV.
  • 11.6K
  • 31 Oct 2022
Topic Review
Electron-beam Technology
Since the mid-20th century, electron-beam technology has provided the basis for a variety of novel and specialized applications in semiconductor manufacturing, microelectromechanical systems, nanoelectromechanical systems, and microscopy.
  • 456
  • 29 Sep 2022
Topic Review
Electrostatic Dust Cloth
Electrostatic dust cloths (EDC) have been widely used for microbiologic contamination assessment in different indoor and occupational environments. Electrostatic dust cloths are negatively charged allowing dust particles to settle with greater ease.
  • 1.3K
  • 31 Mar 2022
Topic Review
Electrostatic Fluid Accelerator
An electrostatic fluid accelerator (EFA) is a device which pumps a fluid such as air without any moving parts. Instead of using rotating blades, as in a conventional propeller or in the turbine of an airbreathing jet engine, an EFA uses the Coulomb force from a high voltage electric field to accelerate electrically charged air molecules, a phenomenon studied in the academic discipline called electrohydrodynamics (EHD). Because air molecules are normally electrically neutral, not charged, the EFA has to create some charged molecules, or ions, first. Thus there are three basic steps in the fluid acceleration process: ionize air molecules, accelerate those charge carriers and, through ion-ion and ion-neutral collisions, push many more neutral molecules in a desired direction, and finally neutralize ions again to eliminate any net charge in the downstream flow. This principle is used for spacecraft propulsion in ion thrusters. The basic working principle has been understood for some time but only in recent years have seen developments in the design and manufacture of EFA devices that may allow them to find practical and economical applications, such as in micro-cooling of electronics components.
  • 864
  • 31 Oct 2022
Topic Review
Electrostatic Nuclear Accelerator
An electrostatic nuclear accelerator is one of the two main types of particle accelerators, where charged particles can be accelerated by subjection to a static high voltage potential. The static high voltage method is contrasted with the dynamic fields used in oscillating field particle accelerators. Owing to their simpler design, historically these accelerators were developed earlier. These machines are operated at lower energy than some larger oscillating field accelerators, and to the extent that the energy regime scales with the cost of these machines, in broad terms these machines are less expensive than higher energy machines, and as such they are much more common. Many universities worldwide have electrostatic accelerators for research purposes.
  • 1.0K
  • 25 Oct 2022
Topic Review
Elementary Charge and Vacuum Energy
Classical electrodynamics was introduced by James Clear Maxwell nearly 150 years ago and it is a subject that had been thoroughly explored over these years. Notwithstanding this long term scrutiny of this subject, there are hidden features in classical electrodynamics that actually heralds the emergence of Quantum electrodynamics in the future. Such examples can be found when analyzing the electromagnetic radiation generated by antennas working in both frequency and time domain and in the case of transition radiation generated by decelerating electrons. Here we discuss one such case. Consider the radiation generated by an antenna working in frequency domain. One can show that the energy dissipated as radiation within half a period of oscillation, say U, satisfies the inequality U ≥ hf →q ≥ e where q  is the magnitude of the oscillating charge in the antenna, e is the elementary charge, f is the frequency of oscillation and h is the Planck constant. This result is derived while adhering strictly to the principles of classical electrodynamics alone. Combining this result with the concept of photons burrowed from quantum mechanics, one can derive an expression for the elementary charge as a function of other natural constants and the energy density of vacuum. The expression predicts the value of elementary charge to an accuracy higher than about 0.1%.
  • 1.3K
  • 01 Nov 2020
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