A The Effect of Current on Cell Potential

Usually we try to minimize the IR drop in the cell by having a very small cell resistance (high ionic strength) or by using a special three-electrode cell (see Section 22C-2), in which the current passes between the working electrode and an auxiliary electrode, or counter electrode. With this arrangement, only a very small current passes between the working electrode and the reference electrode, which minimizes the IR drop. 

The following cell has been used for the determination of cadmium in the presence of chloride ions by both electrogravimetry and coulometry. 

Calculate the potential that (a) must be applied to prevent a current from developing in the cell when the two electrodes are connected and (b) must be applied to cause an electrolytic current of 2.00 mA to develop. Assume that the internal resistance of the cell is 15.0 O. 

Direct current (dc) is current that is always in one direction it is unidirectional. The direction of alternating current (ac) reverses periodically. 

Note that a plot of current in an electrolytic cell versus applied potential should be a straight line with a slope equal to the negative reciprocal of the resistance, — l/R, 

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