Wednesday, January 16, 2008


A battery is a device in which the energy of a chemical reaction is converted into electricity. This is accomplished by immersing two metals in an electrolytic solution, where the electrolyte, a non metallic conductor, dissociates into charged components, or ions. The metals must be chosen according to their electrochemical activity, which depends on their ability to gain or lose electrons. This gain or loss causes a potential difference or voltage, between the two metals. When the metal are connected by an external circuit to a load such as light bulb, a current of electrons will flow from one metal (the anode), through the wire and the load, to the other metal (the cathode). Ion carry the current through the electrolyte solution and complete circuit.

In regard to electron current moving through the wire and load, the anode is negative the cathode positive. In regard to the ion current, the anode is positive and the cathode negative, since the positive ion coat the anode and make it appear positive. It is standard to table the electrodes in regard to the electron current. In either case, the anode is the metal that give up electrons to the wire and positive ions to the solution, and the cathode accept electrons from the wire and positive ions from the solution.

Battery differ from fuel cell in that they contain all the chemicals to be used in the reaction, fuel cells are supplied with these reactants from an outside source. A battery in which the reactions are not readily reversible is called a primary battery. If they can be reversed by the passage of current in the opposite direction, the battery is called a secondary, or storage, battery. Although, theoretically, many combination of electrochemical reactions are possible in primary batteries, only a few have been successfully realized, and fewer yet are sufficiently reversible for satisfactory secondary cell.

The simple cell has a lead anode (+) and a lead dioxide cathode (-), immersed in sulfuric acid. As current flow through the wire from anode to cathode, it light the bulb. A cell in storage battery has several positive and negative plate, separated porous insulators.

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