|Working principle||Electrochemical reactions, Electromotive force|
The symbol for a battery in a circuit diagram. It originated as a schematic drawing of the earliest type of battery, a voltaic pile.
A battery really means two or more wet or dry cells connected in series for more voltage, or in parallel for more current, although people often call a cell a battery. AA, AAA, C, and D batteries all have 1.5 volts. The voltage of a cell depends on the chemicals used while the amount of power or current it can supply also depends on how large the cell is; a bigger cell of a given type can supply more amps, or for a longer time.
The chemical reactions that occur in a battery are exothermic reactions and, thus, produce heat. For example, if you leave your laptop on for a long time, and then touch the battery, it will be warm or hot. However, the batteries used in laptops are called Lithium batteries and they do have a fire hazard (A few years ago, dell laptops that that were powered by lithium batteries began to catch fire, though this event was rare.).
Batteries are always more costly/expensive than mains electricity. But mains electricity is not suitable for things that are mobile.
Hand and foot generators can be used to replace batteries, but they can be tiresome.
Since clockwork clocks have been around for hundreds of years, and batteries for two hundred, it is amazing that no-one thought of a clockwork torch until recently.
Rechargeable batteries are recharged by reversing the chemical reaction that occurs within the battery. Although, a rechargeable battery can only be recharged a given amount of time (recharge life). Even iPods, with built in batteries, cannot be recharged forever. Moreover, each time you recharge a battery, its ability to hold a charge is degraded a bit. Never attempt to recharge a non-rechargeable battery, the battery acids inside will most likely leak out.
The very first batteries were invented in the middle east around 1000 B.C.
Later batteries were bottles with a fluid and some metal rods in them. People had to be careful not to turn these batteries upside-down so the fluid would spill.
In modern batteries, the fluid is "soaked up" in a kind of paste. And everything is put in a completely tight case: Because of this case, nothing can spill out of the battery.
Batteries come in many different shapes, sizes and voltages.
AA, AAA, C, and D cells, including alkaline batteries, are of standard sizes and shapes, and have about 1.5 volts. The voltage of a cell depends on the chemicals used. The electric charge it can supply depends on how large the cell is, as well as what chemicals. The charge a battery delivers is usually measured in ampere-hours. Since the voltage stays the same, more charge means a bigger cell can supply more amps, or run for a longer time.
Alternatives to batteries
A capacitor is not a battery because it does not store the energy in a chemical reaction. A capacitor can store electricity and create electricity much faster than a battery, but it usually costs too much to make it as big as a battery can be. Scientists and chemical engineers are working to make better capacitors and batteries for electric cars.
Small electrical generators operated by hand and foot can supply power in small electrical devices. Clockwork radios, clockwork torches and similar devices also have a wind-up spring to store mechanical energy.
Battery Facts for Kids. Kiddle Encyclopedia.