electrode(redirected from needle electrode)
Also found in: Dictionary, Thesaurus, Medical.
electrode,terminal through which electric current passes between metallic and nonmetallic parts of an electric circuit. In most familiar circuits current is carried by metallic conductors, but in some circuits the current passes for some distance through a nonmetallic conductor. For example, in electrolysiselectrolysis
, passage of an electric current through a conducting solution or molten salt that is decomposed in the process. The Electrolytic Process
The electrolytic process requires that an electrolyte, an ionized solution or molten metallic salt, complete an
..... Click the link for more information. current passes through a liquid electrolyte; in a fluorescent lamp current passes through a gas. An electrode is usually in the form of a wire, rod, or plate. It may be made of a metal, e.g., copper, lead, platinum, silver, or zinc, or of a nonmetal, commonly carbon. The electrode through which current passes from the metallic to the nonmetallic conductor is called the anode, and that through which current passes from the nonmetallic to the metallic conductor, the cathode. (Electron flow is in a direction opposite that of conventionally defined current.) In most familiar electric devices, current flows from the terminal at higher electric potential (the positive electrode) to the terminal at lower electric potential (the negative electrode); therefore, the anode is usually the positive electrode and the cathode the negative electrode. In some electric devices, e.g., an electric battery, nonelectric energy is converted to electric energy, causing current to flow within the device from the negative electrode to the positive electrode, so that the anode is the negative electrode and the cathode is the positive electrode.
a structural component of an electronic, ion, or electrical engineering device or production apparatus. It consists of a conductor with a specific shape, which connects a section of an electric circuit in contact with a working medium—a vacuum (in the practical sense), gas, semiconductor, or liquid—to the remainder of the circuit (which is formed by conductors).
The electrodes of electronic devices (electron tubes, electronbeam instruments, semiconductor devices, and so on) are usually in the form of a plate, grid, cylinder, or the like. They have a wide variety of functions. For example, as cathodes and photocathodes, they act as sources of electrons; as grids (control, shield, and suppressor types) and the electrodes of electron guns, they are used to create within a device electric fields that control the motion of electrons and ions in the working medium; as anodes (plates), they collect electrons.
in electrochemistry, a metal, oxide, or other electrical conductor in contact with an ionic conductor, such as an electrolytic solution or a fused electrolyte. The most important characteristic of electrodes is the electrode potential established at the electrode-electrolyte boundary. Depending on use, electrodes may be classified as reference, indicator, and other types. Systems of two different electrodes can be used as chemical sources of current; when direct current passes through such systems, they act as electrolytic cells.