Depending on the type of system, an anode can be positively or negatively charged, although in most cases it is positively charged.
An anode is the electrode in an electrical system through which electrical current enters the system. Depending on the type of system, this electrode can be positively or negatively charged, since in most cases it is positively charged. Anodes are electrically charged components of batteries and tanks that are used to polarize or deposit layers of various metals. There are also various devices that use special types of electrodes, called sacrificial anodes, to protect other metal components.
Batteries, which are galvanic cells, use anodes to transmit energy from the chemical process within the cell to the device that requires power. Although most anodes are positively charged, in this case the anode is the negative side of the battery. In these devices, the metal of this electrode slowly dissolves in the liquid as part of the chemical reaction that takes place in the battery. Once the electrode is completely dissolved, the battery has no more power, although batteries that are capable of recharging change the role of anode and cathode during charging, allowing metal to redeposit on the anode.
Devices like cathode ray tubes and diodes also use anodes. In these cases, the anodes are on the positive side of the electrical system. Power travels to these types of systems through the anode and out through the diode. As energy enters the system in this way, electrons leave the system through the anode.
Sacrificial anodes are used in devices such as water heaters. They get their name from the way they are “sacrificed” to preserve other materials in the device, such as the metal tank of the water heater. The electricity used to power this type of device causes the metal components to break down over time, so sacrificial anodes are attached to them to prevent the other metal components from deteriorating. As long as the anode is made of a more “active” metal than the metal in the rest of the device, it will deteriorate instead of the other metals. In some cases, the presence of a less active metal can accelerate the deterioration of the anode metal, meaning it may need to be replaced more frequently.