Measurement unit of current. Symbol: "A" or "amp".
anode
The electrode where oxidation occurs in an electrochemical cell. It is the positive electrode in an electrolytic cell, while it is the negative electrode in a galvanic cell. The current on the anode is considered a positive current according to international convention; however, in electroanalytical chemistry the anodic current is often considered negative. Contrast with cathode.
anion
A negatively charged ion.
ac
Stands for alternating current. However this term is also used in connection with ac voltage, that is, an "alternating" voltage that will cause an "ac current" to flow in a conductor, and also in connection with ac power.
atom
The atom is a basic unit of matter consisting of a dense, central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons (except in the case of hydrogen-1, which is the only stable nucleide with no neutron).
cathode
The electrode where reduction occurs in an electrochemical cell. It is the negative electrode in an electrolytic cell, while it is the positive electrode in a galvanic cell. The current on the cathode is considered a negative current according to international convention; however, in electroanalytical chemistry the cathodic current is often considered positive.
cation
A positively charged ion.
current
The movement of electrical charges in a conductor; carried by electrons in an electronic conductor (electronic current) or by ions in an ionic conductor (ionic current). "By definition" the electrical current always flows from the positive potential end of the conductor toward the negative potential end, independent of the actual direction of motion of the differently charged current carrier (or "charge carrier") particles. Two kinds of currents must be distinguished: "direct current (dc)" and "alternating current (ac)". Direct current is the unidirectional continuous flow of current, while alternating current is the oscillating (back and forth) flow of current. In electrochemistry, we almost always use direct current. Consequently, the term "current" always designates "dc" in this dictionary unless specifically stated to be "ac". The normal household current is an alternating current. The measurement unit of current is the ampere.
As mentioned above, the "defined" current flows from the positive terminal of the current source, trough the load, to the negative terminal of the source. Consequently, inside the "source" (whether it is electromechanical or electrochemical) the current must flow from the negative terminal to the positive terminal since there must be a complete circuit. This concept is especially important in electrochemistry because an electrochemical cell can be either a current "source" (galvanic cell) or a "load" (electrolytic cell). Furthermore, a rechargeable battery operates as a "source" during discharge and as a "load" during charge.
current density
Electroplating current divided by the total surface area of the part. Influences deposition rate, and plating quality. The higher the current density the faster the plating rate will be.
current efficiency
The fraction, usually expressed as a percentage, of the current passing through an electrolytic cell (or an electrode) that accomplishes the desired chemical reaction. Inefficiencies may arise from reactions other than the intended reaction taking place at the electrodes, or side reactions consuming the product. The expected production can be theoretically calculated and compared with the actual production.
counterion
The mobile ion in ion exchange. The ion with opposite charge to that of the fixed site on the ion-exchange resin. Contrast with fixed ion.
