1. battery, voltaic or galvanic An apparatus for converting chemicalenergy directly into electricenergy. This is as broad a definition as can well be given. The generalconception of a battery includes the action of electrolysis, a solution in the batteryacting upon one of two conducting electrodes immersed in such fluid, which dissolves one of them only, or one more than the other. The best way to obtain a fundamental idea of a battery is to start with the simplest. Dilute sulphuric acid dissolves neither pure zinc nor copper. But it has a far stronger affinity for the first named metal. If now we immerse in dilute acid two plates, one of pure zinc, and one of copper, no action will be discernible. But if the plates are brought in contact with each other a stream of bubbles of hydrogen gas will escape from the surface of the copper and the zinc will dissolve. By applying proper tests and deductions it will be found that the copper and zinc are being constantly charged with opposite electricities, and that these are constantly recombining. This recombination produces what is known as an electric current.
To constitute a battery the zinc and copper plates must be connected outside of the solution. This connection need not be immediate. Any conductor which touches both plates will bring about the action, and the current willpass through it.
The easiest way to picture the action of a battery is to accept the doctrine of contact action. In the battery the molecules of water are pulled apart. The hydrogen molecules go to the copper, the oxygen molecules go to the zinc, each one, leaving its contact with the other, comes off charged with oppositeelectricity. This charges the plates, and the continuous supply of charge and its continuous discharge establishes the current.
To this concretenotion of a voltaicbattery the different modifications described here may be referred. Zinc, it will be seen, forms the almost universally used dissolved plate; carbon or copper forms the most usual undissolved plate; sulphuric acid in one form or another is the most usual excitant.
It is not necessary to have electrodes of different substances, the samemetal maybe used for both if they are immersed in different solutions which act differentially upon them, or which act with moreenergy on one than on the other. Such are only of theoretical interest.
Definitions of battery, voltaic or galvanic
