Potential across

Fig. XIV-5. Variation in potential across an oil-water interface (a) in the absence of electrolyte, (b) with electrolyte present, and (c) in the presence of soap ions and a large amount of salt. (From Ref. 35.)...

If a gas such as argon is held in a glass envelope that has two electrodes set into it (Figure 6.4), application of an electric potential across the electrodes leads to changes in the gas as the electrons flow from the cathode (negative electrode) to the anode (positive electrode). This passage of electrons... 

Fig. 1. The structure of the electrical double layer where Q represents the solvent CD, specifically adsorbed anions 0, anions and (D, cations. The inner Helmholtz plane (IHP) is the center of specifically adsorbed ions. The outer Helmholtz plane (OHP) is the closest point of approach for solvated cations or molecules. O, the corresponding electric potential across the double layer, is also shown.

The photoreceptor must be stable in performance. In order to guarantee that the quaUty of copies stays the same after hundreds of thousands of produced copies, the photoreceptor should maintain the same charge acceptance. That is, the potential across the photoreceptor should be the same... 

Galvanic cells in which stored chemicals can be reacted on demand to produce an electric current are termed primaiy cells. The discharging reac tion is irreversible and the contents, once exhausted, must be replaced or the cell discarded. Examples are the dry cells that activate small appliances. In some galvanic cells (called secondaiy cells), however, the reaction is reversible that is, application of an elec trical potential across the electrodes in the opposite direc tion will restore the reactants to their high-enthalpy state. Examples are rechargeable batteries for household appliances, automobiles, and many industrial applications. Electrolytic cells are the reactors upon which the electrochemical process, elec troplating, and electrowinning industries are based. 

A unique application of the solid oxygen electrolytes is in dre preparation of mixed oxides from metal vapour deposits. For example, the ceramic superconductors described below, have been prepared from mixtures of the metal vapours in the appropriate proporhons which are deposited on the surface of a solid electrolyte. Oxygen is pumped tluough the electrolyte by the application of a polarizing potential across the electrolyte to provide the oxidant for the metallic layer which is formed. 

Flanged Elliptical Opening The potential flow solution for an elliptical aperture in an infinite wall with a constant potential across the hood face is given by Lamb as... 

The orientational structure of water near a metal surface has obvious consequences for the electrostatic potential across an interface, since any orientational anisotropy creates an electric field that interacts with the metal electrons. Hydrogen bonds are formed mainly within the adsorbate layer but also between the adsorbate and the second layer. Fig. 3 already shows quite clearly that the requirements of hydrogen bond maximization and minimization of interfacial dipoles lead to preferentially planar orientations. On the metal surface, this behavior is modified because of the anisotropy of the water/metal interactions which favors adsorption with the oxygen end towards the metal phase. 

Instead of an exact calculation, Gouy and Chapman have assumed that (4) can be approximated by combining the Poisson equation with a Boltzmann factor which contains the mean electrical potential existing in the interface. (This approximation will be rederived below). From this approach the distribution of the potential across the interface can be calculated as the function of a and from (2) we get a differential capacitance Cqc- It has been shown by Grahame that Cqc fits very well the measurements in the case of low ionic concentrations [11]. For higher concentrations another capacitance in series, Q, had to be introduced. It is called the inner layer capacitance and it was first considered by Stern [1,2]. Then the experimental capacitance Cexp is analyzed according to ... 

Most devices are designed for a constant potential and, as a result, power is usually distributed to loads at constant potential. Two possible configurations for delivering a constant potential to multiple loads are illustrated in Figure 2-73. In the parallel circuit, the potential across the load decreases as the distance from the source increases. For the loop circuit, potentials are more nearly equal along the length of the circuit. 

As indicated in Fig. 21.3, for both atomic absorption spectroscopy and atomic fluorescence spectroscopy a resonance line source is required, and the most important of these is the hollow cathode lamp which is shown diagrammatically in Fig. 21.8. For any given determination the hollow cathode lamp used has an emitting cathode of the same element as that being studied in the flame. The cathode is in the form of a cylinder, and the electrodes are enclosed in a borosilicate or quartz envelope which contains an inert gas (neon or argon) at a pressure of approximately 5 torr. The application of a high potential across the electrodes causes a discharge which creates ions of the noble gas. These ions are accelerated to the cathode and, on collision, excite the cathode element to emission. Multi-element lamps are available in which the cathodes are made from alloys, but in these lamps the resonance line intensities of individual elements are somewhat reduced. 

Neuromuscular junction (NMJ) is the synapse or junction of the axon terminal of motoneurons with the highly excitable region of the muscle fibre s plasma membrane. Neuronal signals pass through the NMJ via the neurotransmitter ACh. Consequent initiation of action potentials across the muscle s cell surface ultimately causes the muscle contraction. 

Voltage-gated potassium (Kv) channels are membrane-inserted protein complexes, which form potassium-selective pores that are gated by changes in the potential across the membrane. The potassium current flow through the open channel follows by the electrochemical gradient as defined by the Nernst equation. In general, Kv channels are localized in the plasma membrane. 

FIGURE 1-12 Variation of the potential across the electrical double layer. 

The redox carriers are grouped into respiratory chain complexes in the inner mitochondrial membrane. These use the energy released in the redox gradient to pump protons to the outside of the membrane, creating an electrochemical potential across the membrane. 

The following factors affect net diffusion of a substance (1) Its concentration gradient across the membrane. Solutes move from high to low concentration. (2) The electrical potential across the membrane. Solutes move toward the solution that has the opposite charge. The inside of the cell usually has a negative charge. (3) The permeability coefficient of the substance for the membrane. (4) The hydrostatic pressure gradient across the membrane. Increased pressure will increase the rate and force of the collision between the molecules and the membrane. (5) Temperature. Increased temperature will increase particle motion and thus increase the frequency of collisions between external particles and the membrane. In addition, a multitude of channels exist in membranes that route the entry of ions into cells. 

The surface potential of a liquid solvent s, %, is defined as the difference in electrical potentials across the interface between this solvent and the gas phase, with the assumption that the outer potential of the solvent is zero. The potential arises from a preferred orientation of the solvent dipoles in the free surface zone. At the surface of the solution, the electric field responsible for the surface potential may arise from a preferred orientation of the solvent and solute dipoles, and from the ionic double layer. The potential as the difference in electrical potential across the interface between the phase and gas, is not measurable. However, the relative changes caused by the change in the solution s composition can be determined using the proper voltaic cells (see Sections XII-XV). 

The second effect is that of a change in the potentiaf difference effectively influencing the reaction rate. By its physical meaning, the activation energy should not be influenced by the full Galvani potential across the interface but only by the potential difference (cpo ) between the electrode and the reaction zone. Since the Galvani potential is one of the constituent parts of electrode potential E, the difference - j/ should be contained instead of E in Eq. (14.13) ... 

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