Electrode is a conductor through which current enters or leaves an electric or electronic device. Most electrodes are pieces of metal shaped into plates, rods, wires, or wire mesh.
A battery has two electrodes—one positively charged and one negatively charged. When they are connected to an external circuit, the battery produces current.
Vacuum tubes and solid-state electronic devices have two or more electrodes. Voltages are applied to the electrodes from the outside, and the electrodes establish and maintain the desired voltages and electric fields within the device. The flow of current within the device can be controlled by varying the voltages applied to the electrodes.
See also Battery; Electrolysis; Neon; Vacuum tube.
