Anode current flows into "the device" (i.e. the battery cell). This inward current is carried externally by electrons moving outwards, negative charge flowing in one direction being electrically equivalent to positive charge flowing in the opposite direction. In a recharging battery, or an electrolytic cell, the anode is the positive terminal, which receives current from an external generator. The current through a recharging battery is opposite to the direction of current during discharge; in other words, the electrode which was the cathode during battery discharge becomes the anode while the battery is recharging. In a diode, the anode is the positive
Plate electrode tube envelope and is cooled by radiation cooling, forced air or water. A problem in early vacuum tubes was "secondary emission"; electrons striking the plate could knock other electrons out of the metal surface. In some tubes such as tetrodes these "secondary electrons" could be absorbed by other electrods such as grids in the tube, resulting in a current out of the plate. This current could cause the plate circuit to have negative resistance, which could cause unwanted parasitic oscillations. To prevent this most plates in modern tubes are given a chemical coating which reduces secondary emission. Plate electrode A