A voltaic cell is a device made from connecting two different metals together and immersing the combined piece into some sort of fluid that creates a conductive atmosphere. The general purpose of a voltaic cell is to convert the chemical reaction between the metals and the fluid into an electrical charge. One of the most common examples is simply a battery, used to supply electrical power to devices not connected to a central grid power source.
The basic way a voltaic cell works is by utilizing the galvanic technique. A galvanic voltaic cell consists of two metals, such as copper and zinc, placed very close to each other. This unified piece is then covered in salt water, which causes the electrochemical reaction to occur. The key behind the reaction comes from the fact that the metal contains cations, ions with more protons than electrons. Cations react with the water, which contains anions, ions with more electrons than protons.
It is necessary to keep both metals separated by a small barrier. This is because one metal will cause the reduction of oxidation within the other, while the other metal increases oxidation. The reaction between both the cations and the anions creates an exchange of electrons and thereby, the creation of electricity.
When a number of these galvanic voltaic cells are placed in a series, it is referred to as a voltaic pile. Alternating the two metals with some sort of electrolyte barrier can create the electrochemical reaction. If the two ends of the voltaic pile are connected, an electrical current will be created, which can then be used to power other devices in the form of a battery.
One of the side effects of the voltaic reaction is corrosion. Due to the continued chemical reaction, the electron exchange ultimately causes the metals to degrade. This is why a battery eventually goes dead rather than lasting forever.
The use of the voltaic cell appears to date back to ancient times with the discovery of the Baghdad Battery in 1936, a series of galvanic cells placed in large jars from sometime in the first few centuries AD. However, it wasn't until the work of Luigi Galvani in the late 1700s that battery technology was modernized. Galvani found that by connecting copper and zinc together, he was able to make the muscles in a frog's leg spasm. Alessandro Volta took this information and adapted it to the voltaic pile in 1800.