Specific resistance, definition

In the above relationship p is an intrinsic property called the specific resistance (or resistivity) of the conductor. The definition of the specific resistance of any given conductor follows from this relationship. It is the resistance in ohms of a specimen of the material, 1 cm long and 1 cm2 in cross-sectional area (units ohm cm-1), the length being in the direction of the current and the cross-section normal to it. In other words, the specific resistance p of a conductor is the resistance of a cube of 1 centimeter edge. If the conductance is denoted by C = 1 /R, then the specific conductance (or conductivity) K, is given by JC= 1/a (units ohm-1 cm-1, mho cm-1, reciprocal ohm cm-1). Therefore, the relationship R = aL/A may be written as R = L/KA (units ohms) and the conductance can be expressed as C = 1/R = KA/l (units reciprocal ohms). 

The Specific conductance of any conducting material is defined as th( reciprocal of the specific resistance it is given the symbol k and is stated in reciprocal ohm units, sometimes called mhos/ Since, by definition, K is equal to 1/p, it follows from equation (1) that... 

The difference in the temperature of the electrolyte at entrance and exit of the lEG during cross-flow technique is an important factor. Rise in the temperature of electrolyte tends to decrease its specific resistance but in contrast to that, the insoluble gas and vapor bubbles increases the resistance as shown in Fig. 7.14. However, in EMM the length of the lEG is very small. In such situations temperature rise will increase the conductivity of electrolyte. But these changes would definitely affect the microfluctuation of flow rate and pressure characteristics of the electrolyte in the lEG. There are many advantages of using hot electrolyte too. An increase in the temperature increase the conductivity and in... 

Again using the concpt of a uniform specific resistance throughout the filter cake, rearranging Equation (2.39) and using the definition of constant rate (dV/dt = V/t) ... 

Ibl carries the argument on equalizing action of overvoltage a step further. As we have seen, current distribution is more uniform when ratio RJRg is greater. Now R is the resistance of the solution per m of cross-sectional area, and is given by the specific resistance times the distance between the two electrodes (d). Expressed in terms of the specific conductivity K, Rg = d/K. Remembering the definition of R , we obtain ... 

On the other hand, the values of the resistance per layer showed a definite increase with the thickness of the film. The specific resistance of the films thus determined from their values of the resistance per layer was ca. 10 fl. This was based on the results of capacity measuranents on some 75 samples. The capacitance measurements thus performed on stearate films (1-10 layers) led to e values between 2.1 and 4.2, with a bulk value of 2.5. 

Conductivity. The standard unit of conductance is electrolytic conductivity (formerly called specific conductance) k, which is defined as the reciprocal of the resistance of a 1-m cube of liquid at a specified temperature m— ]. See Table 8.33 and the definition of the cell constant. 

Corrosion Resistance. The environment to which a plated part is to be exposed should be a part of any definition of corrosion resistance. Problems arise in testing a part in its intended environment in part because of the long time period required. In many plating processes, corrosion resistance is direcdy proportional to the plate thickness, so a specification on plate thickness is a much faster method of indirectiy measuring corrosion resistance. In specifying a corrosion resistance requirement for the production of plated goods, accelerated tests are used especially if plate thicknesses caimot be related to corrosion protection. 

Table IV summarizes the results for the resist screening studies at SSRL. The resist candidates generally exhibited good sensitivity, Dg 5 < 50 mJ/cm2, and contrast, 7 = 1.5. Definitive conclusions regarding the effect of structure on sensitivity are made difficult by the fact that polymer molecular weight and poly-dispersity varied considerably from sample to sample and, since we found a very strong dependence of Dg 5 on these parameters, specific structural effects are obscured. Several generalizations can be made, however.

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