Conductivity, electrical equivalent conductance

The phenomena important in electrolytic conductance have been discussed96 and are represented by the electrical equivalent circuit of a conductance cell shown in Figure 6.24a. 

Figure 6.24 (a) Electrical equivalent circuit for a conductance cell (b) AC bridge with the cell impedance balanced by a series R-C combination (c) AC bridge with the cell impedance balanced by a parallel R-C combination (see Table 6.7). 

The complications and sources of error associated with the polarization resistance method are more readily explained and understood after introducing electrical equivalent circuit parameters to represent and simulate the corroding electrochemical interface (1,16-20). The impedance method is a straightforward approach for analyzing such a circuit. The electrochemical impedance method is conducted in the frequency domain. However, insight is provided into complications with time domain methods given the duality of frequency and time domain phenomena. The simplest form of such a model is shown in Fig. 3a. The three parameters (Rp, Rs, and C d,) that approximate a corroding electrochemical inter-... 

Electret. The electrical equivalent of a permanent magnet. When a block of dielectric material, such as carnauba wax, is allowed to be solidified in a strong electric field it acquires a permanent state of electrostatic polarization (orientation of molecules) in the direction of the field. Swann (Ref 3) traced the mathematical consequences on the assumption that an electret consists of a) a distribution of polarization which decays with time and b) a distribution of surface volume chge which disappears acedg to ohmic conductivity having no relation to the decay of polarization Refs 1) Hackh s Dict(1944), 296-L 2) F. 

Other factors that increase throwing power are higher bath conductivity, which makes it easier to get electricity into recesses, and higher electric equivalent weight of the paint, which gives more deposit per unit of electricity (coulomb). 

More detailed information on the physical structure and electrical properties can be obtained by analysis of the impedance spectra, as presented in Figure 6. An electrical equivalent circuit [resistance-capacitance (RC) circuit] was used by Fare (38) to interpret the capacitance and conductance data of... 

The radioelectric properties of two composites based on polyaniline impregnated glass textiles with different conductivities have been characterised. Changes of (fi. e") with frequency are shown in Figure 8.41. A dependence quite different from those already presented is observed. Indeed, for both conductivities, log e" decreases linearly with log/ with a slope close to unity, e.g., 0.7 and 0.8. This behaviour, independent of conductivity, is representative of a purely resistive material. The electrical equivalent circuit was found to be a resistance in parallel with a capacitance [84,86]. 

Fig. 3A-C. Representations of the differential-charging effect. A Heterogeneous sample consisting of conducting base (black) and a structured insulating surface (grey). The arrows depict schematically current trajectories for different spots of the sample denoted by the indices 1,2, 3 (11,12,13 - emitted currents). Due to different resistance properties, different potentials Ui, U2, U3 arise. B Electrical equivalence diagram for a sample under constant irradiation. C Effect of differential charging on the position of the energy scale of the photoemission experiment...

Electrical circuits are used to model the electrical behavior of neurons. These electrical-equivalent circuits, often referred to as cable models, represent the neuron as a series of cylindrical elements. Each cylinder is in turn replaced by a compartment, representing the neuronal membrane, and a resistor representing the intracellular space. Thus the model becomes a series of membrane compartments, connected by resistors. Each compartment is itself an electrical circuit that includes a capacitor representing the membrane capacitance of the lipid bilayer, resistors representing the ionic conductances of the transmembrane... 

In view of the above features, oscillometric (conductometric) and potentiometric sensors seem to be best suited for use in industrial and environmental monitors among the electro-analytical techniques. Oscillometric and conductometric sensors fulfil the first and third requirement, the technical problems in connectin with calibration axe not too difficult. There are, however, problems with the fourth requirement, because impedance and the complex dielectric constant both depend on all constituents present, and because these properties do not only depend on one single factor but on several factors. The electrical equivalent circuit for the oscillometric capacities is given in Fig.l. The expression of the h.f. conductance, G, is as follows ... 

Impedance Detection, Fig. 3 Paths of current flow (a) and electrical equivalent (b) of the impedance of cells (a) Paths of current flow in cell suspension, in which te is an extracellular resistance caused by the conductivity of... 

Planar bilayer membranes are characterized by their electrical response since the insulating bilayer membrane and the two conducting ionic solutions are electrically equivalent to a capacitor with the membrane as the dielectric. The current through a capacitor is directly proportional to the rate of change of the voltage on the capacitor, i = C dV/dt. The capacitance, in turn, is related to the thickness of the membrane and its dielectric constant. The membrane capacitance is determined by applying a ramp potential with a constant dV/dt across the membrane to give a constant current that can be converted to the mem-... 

Figure 7.16 provides a heat conduction scheme and an electric equivalent diagram for the sample containing part of the twin calorimeter for a better... 

DETA (dielectric thermal analysis) Electrical equivalent of DMTA but less generally applicable. Characterises motional processes involving dipole reorientation. Mobile-phase content (hence crystallinity). Measurement of conducting polymers over complete working range. Definition of electrical quantities—dielectric permittivity and loss. 

Fig. 5 Simple electrical equivalent circuit diagrams, (a) Each capacitor represents one electrode -which could each, for example, be two sheets of conducting polymer. The contact resistance Rc represents the sum of electrical contact resistances at both electrodes. is the electrolyte or separator resistance. The other two resistors, shown in (b), represent loss of charge due to parasitic reactions. In the literature, typically the equivalent circuit either describes only one electrode or lumps both electrodes into one capacitance. Often, solution and contact resistances are also lumped together...

There are many compounds which do not conduct electricity when solid or fused indicating that the bonding is neither metallic nor ionic. Lewis, in 1916. suggested that in such cases bonding resulted from a sharing of electrons. In the formation of methane CH4 for example, carbon, electronic configuration l.s 2.s 2p. uses the tour electrons in the second quantum level to form four equivalent... 

The specific heat of aqueous solutions of hydrogen chloride decreases with acid concentration (Fig. 4). The electrical conductivity of aqueous hydrogen chloride increases with temperature. Equivalent conductivity of these solutions ate summarized in Table 8. Other physicochemical data related to... 

This computation is also referred to as calculating the zinc equivalent of the alloy. The increase in strength in this alloy series is caused by increased amounts of beta phase in the stmcture. The silicon brasses show similar hardening effects accompanying a second phase. Typical mechanical properties and electrical conductivity for various cast alloys are shown in Table 2. 

Whenever an electrical network has different configurations, such as star and della, it must first be eonveiied to an equivalent star or della before conducting any analysis. As derived above, the following rules of thumb may be applied ... 

---