Origin of the electric potential

The study of the electric device (Chapter 6) has revealed a large capacitive effect at the interface between the soUd electrolyte and the metallic electrode. Such a capacitive effect necessarily results in the presence of charges Q at the level of the electrode, which could induce the appearance of a potential V, so that  

In fact the formation of the chemisorbed species at the surface of the electrodes is not accompanied by a modification of the total charge of the system. The elections involved in the chemisorptions phenomenon are extracted from the metal, and the system remains neutral. Such a system is not similar to a regular electrostatic system, which takes an external supply of charges stemming from the electrodes into account. 

If only the oxygen and charged species [0 ]m located at the surface of the metallic electrodes are taken into account, we note that there is no direct relation between these charged species and the sohd electrolytes. Because of the great quantity of charges in the metal, the charge per unit area induced by the presence of chemisorbed oxygen species is only compensated by a depletion layer, the thickness of which is extremely small in the metal (about several A). 

These species present at the surface of the metal cannot provoke an accumulation of charges at the level of the metal/solid electrolyte interface. 

Only the charged species [0 ]t, which are located at the level of the metal/solid electrolyte interface, are able to produce electrostatic interactions with the charges carriers of the solid electrolyte. Because the electrodes are ideally polarizable, that is, there is no charge or matter transfers between the electrode and the solid electrolyte, the presence of charged species at the level of the three boundary point can easily generate a local reorganization of the charges present in the material. 

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Figure 8. Responses of the multichannel sensor to five taste qualities. The origin of the electrical potential was taken to 1 mM KC1.

Figure 12. Output patterns for eight brands of beer. The origin of the electric potential was taken to some beer Kl.

Physical Chemistry of Solid-Gas Interfaces 10.3.1.2. Origin of the electric potential... 

The excess of the volume charge in the diffuse layer causes the origin of the electric potential liquid solution. It is dependent on the distance y from the Helmholtz layer (Figure 8). The potential (f> is conventionally set zero at a big distance from the wall. The value of the potential in the diffuse layer in the closest vicinity to the Helmholtz layer (y = 0) is called the zeta potential, 4> 0) = When longitudinal driving electric field E is applied, the velocity fEOF of the plug-like EOF is related to the zeta potential by the Helmholtz-Smoluchowski equation ... 

Results of investigations of liquid cells constituted a subject of many discussions or even violent disputes. Historically, the most controversial was the question of the conditions of EMF measurements, as well as the Beutner [26, 34] - Baur [35] dispute concerning the principle and origin of the electrical potentials under investigation. 

The origin of the ohmic potential difference was described in Section 2.5.2. The ohmic potential gradient is given by the ratio of the local current density and the conductivity (see Eq. 2.5.28). If an external electrical potential difference AV is imposed on the system, so that the current I flows through it, then the electrical potential difference between the electrodes will be... 

Nikolsky and coworkers [275-277] developed a theory of the electric potential at the membrane/electrolyte phase boundary for exchange between the cations in solutions and variously active sites in the membrane. They successfully explained, among other things, the origin of the inflection point on the depen-... 

Equation (1.35) is known as the Debye-Hiickel or Gui-Chapman equation for the equilibrium double layer potential. In terms of the original variable x (1.34), (1.35) suggest e1/2(r(j) is the correct scale of ip variation, that is, the correct scale for the thickness of the electric double layer. At the same time, it is observed from (1.32) that for N 1 the appropriate scale depends on N, shrinking to zero when N — oo (ipm — — oo). This illustrates the previously made statement concerning the meaningfulness of the presented interpretation of relectric potential

(—oo) — 0, < (oo) — —oo). 

The situation is substantially different in the case of chemical modulation of the work function (Janata, 1991). When electrically neutral molecular hydrogen dissociates at the surface and dissolves in palladium, it partially donates charge density to the free electrons in the metal and changes the position of the Fermi level and thus its work function. Consequently, the contact potential between palladium and copper changes as well. The origin of the contact potential is again the distribution of electrons between Pd and Cu, but the cause of this distribution is the interaction between palladium and hydrogen. 

Figure 3 The spatial dependence of the charge density, the electric field, and the electric potential in the semiconductor at equihbrium for an n-type semiconductor/metal junction, where all of the voltage is dropped in the semiconductor space-charge region. The origin of the x-axis is chosen for convenience as the point closest to the interface where the net charge in the semiconductor equals zero, (a) The distance dependence of the charge density under the depletion approximation, (b) The electric field as a function of distance. Note that the maximum electric field occurs at the semiconductor interface, (c) The distance dependence of the electric potential. The electric potential in the bulk of the semiconductor has been defined as zero. Because the sign of the electric field strength is positive, the electric potential at the interface is more negative than in the bulk...

For many years, it has been known that many individual biological cells maintain different distributions in ionic concentrations and an electrical potential difference between their intracellular and extracellular phases at the resting state (Table 19). In some cells, upon application of an appropriate stimulus (electrical depolarization or chemical stimulus), the cells exhibit a time-dependent response via a potential difference across the cell membranes which does not necessarily follow Ohm s law. The former potential is called a resting membrane potential and the latter an excitation potential. We would like to review the origins of these electrical potential differences across the cell membrane. 

Cause and effect. The phenomenon of influence is reversible (in the sense of process direction) a charge can be at the origin of an electric potential in % another pole and, conversely, an electric potential may make a charge appear in... 

The term E° is a constant, as will be discussed with more detail below. The origin of this EMF response is directly related to the sample dependence of the electrical potential difference across the phase boundary between the sample phase and the hydrophobic ion-selective phase. Therefore, before considering any other experimental aspects, let us have a closer look at the phase boundary between ionophore-doped hydrophobic phases and aqueous samples. While Section 3.1.3 will briefly comment on the role of the... 

The alternating behaviour was thus attributed to an influence of the electric potential of the outer layer on the inner multilayer system. As potential origins of this odd/even effect not compensated charges within the multilayer assembly were discussed, which can lead to a reversible swelling and de-swelling, controlled by the surface potential. An alternative... 

The thermodynamic forces could be originated from the gradients of the electric potential by line-integral, expressed by the Kirchhoff s second law. 

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