Everything about Cell Electricity totally explained
In electronics, a
battery is two or more
electrochemical cells which store chemical
energy and make it available as electrical energy. Common usage has evolved to include a single electrical cell in the definition. There are many types of electrochemical cells, including
galvanic cells,
electrolytic cells,
fuel cells,
flow cells and
voltaic piles. A battery's characteristics may vary due to many factors including internal chemistry,
current drain and temperature.
One common division of batteries distinguishes two types:
primary (disposable) and
secondary (rechargeable). Primary batteries are designed to be used once only because they use up their chemicals in an effectively irreversible reaction. Secondary batteries can be recharged because the chemical reactions they use are
reversible; they're recharged by running a charging current through the battery, but in an opposite direction to the discharge current. Secondary, also called
rechargeable batteries can be charged and discharged many times before wearing out. After wearing out some batteries can be
recycled.
Although an
early form of battery may have been used in antiquity, the modern development of batteries started with the
Voltaic pile, invented by the Italian physicist
Alessandro Volta in 1800. Since then, batteries have gained popularity as they became portable and useful for many purposes. The widespread use of batteries has created many
environmental concerns, such as toxic metal pollution. Many reclamation companies
recycle batteries to reduce the number of batteries going into landfills.
History
The modern story of the battery begins in the 1780s with the discovery of "animal electricity" by
Luigi Galvani, which he published in 1791. He created an electric circuit consisting of two different metals, with one touching a frog's leg and the other touching both the leg and the first metal, thus closing the circuit. In modern terms, the frog's leg served as both electrolyte and detector, and the metals served as electrodes. He noticed that even though the frog was dead, its legs would twitch when he touched them with the metals.
Volta realized that the frog's moist tissues could be replaced by cardboard soaked in salt water, and the frog's muscular response could be replaced by another form of electrical detection. He already had studied the electrostatic phenomenon of
capacitance, which required measurements of electric charge and of electrical potential. Building on this experience Volta was able to detect electric current flow through his system, now called a
voltaic cell, or cell for short. The terminal voltage of a cell that isn't discharging is called its
electromotive force (emf), and has the same unit as electrical potential, named (
voltage) and measured in
volts, in honor of Volta. In
1799, Volta invented the battery by placing many voltaic cells in
series, literally piling them one above the other. This
Voltaic Pile gave a greatly enhanced net emf for the combination, with a voltage of about 50 volts for a 32-cell pile. In many parts of Europe batteries continue to be called piles.
Unfortunately, Volta didn't appreciate that the voltage was due to chemical reactions. He thought that his cells were an inexhaustible source of energy, and that the associated chemical effects (for example corrosion) were a mere nuisance, rather than, as
Michael Faraday showed around 1830, an unavoidable consequence of their operation.
While early batteries were of great value for experimental purposes, their limitations made them impractical for a large current drain. Later, starting with the
Daniell cell in
1836, batteries provided more reliable currents and were adopted by industry for use in stationary devices, particularly in telegraph networks where they were the only practical source of electricity, since electrical distribution networks didn't exist then. These wet cells used liquid electrolytes, which were prone to leakage and spillage if not handled correctly. Many used glass jars to hold their components, which made them fragile. These characteristics made wet cells unsuitable for portable appliances. Near the end of the 19th century, the invention of
Dry cell batteries, which replaced liquid electrolyte with a paste, made portable electrical devices practical.
The battery has since become a common power source for many household and industrial applications. According to a
2005 estimate, the worldwide battery industry generates
US$48
billion in sales annually.
How batteries work
A battery is a device that converts chemical energy directly to electrical energy. It consists of one or more voltaic cells. Each voltaic cell consists of two
half cells connected in series by a conductive electrolyte. One half-cell is the positive electrode and the other is the negative electrode. The electrodes don't touch each other but are electrically connected by the electrolyte, which can be either solid or liquid. In many cells, the materials are enclosed in a container, and a separator, which is porous to the electrolyte, which prevents the electrodes from coming into contact.
Each half cell has an electromotive force (or emf), determined by its ability to drive electric current from the interior to the exterior of the cell. The net emf of the battery is the difference between the emfs of its half-cells, as first recognized by Volta. Thus, if the electrodes have emfs
