From Open Energy Information
The positive electrode in an electrochemical cell, or battery.
- An anode is an electrode through which conventional current flows into a polarized electrical device. A common mnemonic is ACID for "anode current into device". The direction of (positive) electric current is opposite to the direction of electron flow: (negatively charged) electrons flow out the anode to the outside circuit.The polarity of voltage on an anode with respect to an associated cathode varies depending on the device type and on its operating mode. In the following examples, the anode is negative in a device that provides power, and positive in a device that consumes power:In a discharging battery or galvanic cell (diagram at right), the anode is the negative terminal because it is where 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 terminal at the tail of the arrow symbol (flat side of the triangle), where current flows into the device. Note electrode naming for diodes is always based on the direction of the forward current (that of the arrow, in which the current flows "most easily"), even for types such as Zener diodes or solar cells where the current of interest is the reverse current.In a cathode ray tube, the anode is the positive terminal where electrons flow out of the device, i.e., where positive electric current flows in., An anode is an electrode through which the conventional current is entering into a polarized electrical device. This contrasts with a cathode, an electrode through which the current is out of an electrical device. A common mnemonic is ACID for "anode current into device". The direction of conventional current (the flow of positive charges) in a circuit is opposite to the direction of electron flow, so (negatively charged) electrons flow out the anode into the outside circuit. In Galvanic cell, the anode is the electrode, which oxidation reaction occurs in.An anode is also the wire or plate having excess positive charge. Consequently, anions will tend to move towards the anode.