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An electric battery is a source of electric power consisting of one or more electrochemical cells with external connections [1] for powering electrical devices. When a battery is supplying power, its positive terminal is the cathode and its negative terminal is the anode. [2] The terminal marked negative is the source of electrons.
The voltaic pile was the first electrical battery that could continuously provide an electric current to a circuit. [1] It was invented by Italian chemist Alessandro Volta , who published his experiments in 1799. [ 2 ]
The two elements involved, iron and chlorine, each change oxidation state; iron from +2 to +3, chlorine from 0 to −1. There are then effectively two half reactions occurring. These changes can be represented in formulas by inserting appropriate electrons into each half reaction:
The value of 2.303 R / F is 1.9845 × 10 −4 V / K , so at T = 25 °C (298.15 K) the half-cell potential will change by only 0.05918 V / ν e if the concentration of a metal ion is increased or decreased by a factor of 10.
The NCC improved Gassner's model by replacing the plaster of Paris with coiled cardboard, an innovation that left more space for the cathode and made the battery easier to assemble. It was the first convenient battery for the masses and made portable electrical devices practical, and led directly to the invention of the flashlight.
The zinc-manganese dioxide dry cell was the first portable, non-spillable battery type that made flashlights and other portable devices practical. The mercury battery using zinc and mercuric oxide provided higher levels of power and capacity than the original dry cell for early electronic devices, but has been phased out of common use due to ...
A secondary cell produces current by reversible chemical reactions (ex. lead-acid battery car battery) and is rechargeable. [citation needed] Lead-acid batteries are used in an automobile to start an engine and to operate the car's electrical accessories when the engine is not running. The alternator, once the car is running, recharges the battery.
Electrons have a negative electrical charge, so the movement of electrons is opposite to that of the conventional current flow. Consequently, the mnemonic cathode current departs also means that electrons flow into the device's cathode from the external circuit. For example, the end of a household battery marked with a + (plus) is the cathode.