If several reactions take place simultaneously at the electrode a partial electrode current density (c.d.) \(j_{k}\) can be assigned to each reaction. It is given by the stoichiometry of the reaction and by the amount of substance of B reacting (per unit time and per unit electrode area) in the reaction considered. The current efficiency of reaction \(k\), \(\varepsilon_{k}\) is defined as the ratio of \(j_{k}\) to the total c.d.: \[\varepsilon_{k}=\frac{j_{k}}{\sum_{m} j_{m}}\] Note that \(\varepsilon_{k}\) may be larger than one if cathodic and anodic reactions take place simultaneously at the same electrode. However, \(\varepsilon_{k}\) still gives correctly the product yield, which is the quantity of industrial interest. The product yield is the amount of substance of B produced per unit charge and is equal to \(\frac{\varepsilon_{k}\ \nu _{B,k}}{n_{k}\ F}\) (in the absence of a chemical reaction which is consecutive to the electrode reaction and which consumes or produces species B). \(n_{k}\) is the charge number of electrode reaction \(k\). Note that in the case of simultaneous electrode reactions the distribution of the partial c.d. \(j_{k}\) may be different from that of the total c.d., i.e. the function \(\frac{\left(j_{k}\right)_{\rm{x}}}{j}=f_{k}\left(x\right)\) may be different from \(\frac{j_{\rm{x}}}{j} = f(x)\). In electroplating the term 'metal distribution' is sometimes used to designate the distribution \(f_{k}\left(x\right)\) of the partial c.d. for metal deposition.