Resistance of electrolytes

In ECM, electrolytes serve as conductors of electricity and Ohm s law also appHes to this type of conductor. The resistance of electrolytes may amount to hundreds of ohms. 

The.se arc similar to stator resistance starters, as discussed in Section 4.2..3 and can be used in the rotor circuit to control the rotor side resistance. Figure 5.10 shows the smooth variation of resistance by electrolytic vaporization compared to a conventional metallic resistance variation. I hc self-variable resistance of electrolyte is equivalent to almost three or four steps of a metallic resistance and makes such starters economical. Normally one step is sufficient for motors up to 160 h.p. (For spccd-torquc... 

It is not usual to talk about the resistance of electrolytes, but rather about their conductance. The specific conductance (K) of an electrolyte is defined as the reciprocal of the resistance of a part of the electrolyte, 1 cm in length and 1 cm2 in cross-sectional area. It depends only on the ions present and, therefore it varies with their concentration. To take the effect of concentration into account, a function called the equivalent conductance, A, is defined. This is more commonly (and conveniently) used than the specific conductance to compare quantitatively the conductivities of electrolytes. The equivalent conductance A is the conductance of that volume of the electrolyte which contains one gram equivalent of the ions taking part in the electrolysis and which is held between parallel electrodes 1 cm apart (units ohm-1 cm4). If V cubic centimeters is the volume of the solution containing one gram equivalent, then the value of L will be 1 cm and the value of A will be V square centimeters, so that... 

On May 29, 1891, Haber appeared for his final examinations in chemistry, physics, and philosophy. Haber performed admirably in philosophy, adequately in his chosen field of chemistry, and poorly in physics. Asked how one would measure the electrical resistance of electrolytes—liquids containing electrically charged... 

Figure 4. Resistivity of electrolyte/metal -powder paste. <- Point at which metal phase conductivity exceeds that of electrolyte. Zinc contains 3.0 % Hg.

Figure 5. Temperature dependences of the bulk resistance of electrolyte grains as found by different researchers 1 - our study, Cc2oGd 2 - Zhan [5], Cc2oSm 3 - Gorelov [7], CejoSm ...

Another problem of lowering operating temperature is the increase in the resistivity of electrolyte. There are two approaches to overcome this... 

The method most widely employed to measure the resistance of electrolyte solutions is the a.c. Wheatstone bridge together with subsidiary equipment to amplify and detect the output signal of the bridge. Shedlovsky has reviewed the experimental techniques and the equipment employed for the measurements. 

FIGURE 27.1 Coulter method. Blood cells are surrounded by an insulating membrane, which makes them non-conductive. The resistance of electrolyte-filled channel will increase slightly as cells flow through it. This resistance variation yields both the total number of cells which flow through the channel and the volume of each cell. 

There is as yet no consolidated opinion as to the optimum electrolyte for lithium-sulfiir batteries. Experiments with solid polymer electrolyte are described, but aprotic electrolyte in a Celgard-type separator commonly used in lithium ion batteries is applied more frequently. A large number of electrolytes has been studied that differ both in solvents and the lithium salt. The greatest acceptance was gained by lithium imide solutions in dioxolane (or in a mixture of dioxolane and dimethoxyethane) and also lithium perchlorate solutions in sulfone. Dissolution of polysulfides in electrolyfe is accompanied by a noticeable increase in viscosity and specific resistance of electrolyte. It is the great complexity of the composition of the electrochemical system and that of the processes occurring therein that prevent as yet commercialization of lithium-sulfiir electrolytes. 

Shortage of electrolyte in dilute solutions can strongly affect the charging-discharge behavior of EDLC. The effect of resistance of electrolyte on the process of charge accumulation in EDLC carbon electrodes with solutions of tetraethyl ammonium tetrafluoroborate (TEABF4) in PC was studied. The charge... 

An equivalent electric circuit in such a pore was modeled by a transmission RC circuit containing similar resistances of electrolyte within a pore with branching electric capacitances C of EDL of similar values within a pore (Fig. 27.1 lb). At high frequencies, the phase angle is 45° and the intercept at the Z axis is equal to solution resistance outside the pore. At the frequency of - 0, extrapolation of the dependence to the Z axis yields the sum of ionic resistance inside the pore structure and outer serial resistance. 

The maximum power of fuel cells H2/O2 and CH3OH/O2 with a membrane based on polymer complexes PBI/H3PO4 [7] was as high as 0.25 W cm at a current density of 700mAcm . The electrical resistance of electrolyte membranes was 0.4 the thickness and surface area of the membranes were 0.01 cm and 1 cm, and the doping level was 500 mol%. The measured electrical resistance of the cell was equivalent to a conductivity of 0.025 S cm It was found that the electrical resistance of the fuel cell is independent of the water content in the gas (water produced at the cathode is sufficient for maintaining the necessary conductivity of the electrolyte). This type of fuel cell was characterised by continuous operation at a current density of 200 mA cm over a period of 200 h (and for longer time periods) without reduction of the membrane performance. 

Ohmic losses. The losses appeared thanks to electrical resistance of electrodes and bipolar plates, and resistance of electrolyte against ion flow are the simplest for understanding and modelling. The value of voltage drop, which is connected mainly with resistance of electrotyte, is equal to electrical current. (Kopriva et al. 2007)... 

Resistivity of electrolyte at 35°C (ohm m) Average wastage rate at 108 Am- (kg A >>- ) Length of trial (days) Note... 

The resistance of electrolytes, and thus electrical conductivity, cannot be measured with direct current on account of the polarization of electrodes and the additional resistances thus arising (which falsify the result). For this reason high frequency (>1000 Hz) alternating current is always used. 

In the above equation pe, Pa, and pc are the respective resistances of electrolyte, anode, and cathode, and 4, 4, and 4 are the respective thickness of electrolyte, anode, and cathode, and contact is any contact resistance present in the system. The most dominant contribution to ohmic resistance is by the electrolyte, which can be expressed as... 

Equation (2.121) describes the linear part of the polarization curves for tin [109], silver [1, 6], and lead [34, 35, 110, 111] deposition, and Eq. (2.122) foresees the inflection point in the cases when rj is low and the resistance of electrolyte is large. Finally, Eq. (2.123) describes the part of the polarization curve after the inflection point characterized by the fast increase of current density with increasing the overpotential (see Chap. 1 Sect. 1.3.1.1). 

Rs = electric resistance of electrolyte, p = electric resistivity of electrolyte, cm L = interelectrode gap, cm. 

Pn Resistivity of electrolytic solution with nonconductive suspensions... 

Typically, the anode consists of small particles of hydride-building alloy held together by a binder and conductive additive (acetylene black) and pressed onto a Ni-foam current collector. The impedance of the particle surface is determined by the charge transfer resistance of hydrogen reduction, double layer capacitance, and the impedance of subsequent solid-state diffusion into the bulk of the particle. To take into account electronic resistance between the particles and ionic resistance of electrolyte in pores, as well as the impedance of the particle surface, we can use the transmission line model of Figure 4.5.9. Because particle shape is best approximated as a sphere, diffusion with spherical boundary conditions, as in Eq. (30) can be used for Za. 

However, it is useful first to illustrate the complexity of such systems by showing a hierarchy of equivalent RC circuits that can be developed, from which an ultimate model of a porous-electrode CR device can be constructed. Note that the behavior of an electrochemical capacitor device is, electrically, far from that of a pure capacitor in its ac response spectrum to AV modulation this is primarily due to the complexity of the distributed, internal connections within the matrix, associated with resistivity of electrolyte channels and the intrinsic resistance of the C microparticles or fibrils and their interparticle contact resistances which usually depend on the pressure applied during fabrication of electrode structures. 

Poor resistance of electrolytic silver-plating cold applied using a pad (disbonding, severe attack on the underlying steel). 

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