Ampere maintained value

A typical example would be a coulometric controlled-potential experiment, where initially a large current exists between the auxiliary and the working electrode (the load of the control amplifier). If a potentiostat is rated to have a maximum output of 20 V at 1 A, it cannot supply more than 20 W of power [power (watts) = current (amperes) x potential (volts)]. If Rt were 100 Q, the potentiostat would not be able to control the potential of the working electrode at -2.0 V (or any other potential for that matter) if 0.5 A were demanded. At least 25 W (I2Rt) of power would be required of the potentiostat for potential control to be maintained. As a result of our 5-W deficiency, the potential of the working electrode would be uncontrolled at a value less than the -2.0 V less than 0.5 A, in fact, would pass through the cell. 

Such concentration polarization of the reference electrode is prevented by maintaining the current density (J amperes/cm ) very low at the reference electrode. This is achieved in practice by making sure that the area of the working electrode in the electrochemical cell is much smaller than the surface area of the reference electrode hence the total current flow will be limited by this much smaller area, and J values for the reference wiU be very small, as desired, to prevent concentration polarization. 

Electric current I, i ampere A An ampere is the intensity of a constant current that, if maintained in two rectilinear parallel conductors of infinite length, of negligible circular section, and placed at a distance of 1 m from one another in vacuum, would produce a force equal to 2 X 10 N per meter of length according to this definition, the value of the constant po is exactly equal to 4x x 10 N/A ... 

A simplification, without loss of precision, is possible if the current can be maintained at a constant value. The quantity of electric charge passed is given, in coulombs, merely by multiplying the magnitude of the current in amperes by the elapsed time in seconds. 

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