« НазадПродовжити »
Chemical Producers of Electricity-Action of Simple Primary Battery
The Dry Cell-Methods of Connecting Dry Cells-Discovery of Reversible Chemical Action-Secondary Batteries—Simple Lead_Plate Type-Planté, or Formed Plates-Faure, or Pasted Plates-Edison Non-acid Battery Action.
Current Production by Chemical Action.—The earliest known method of continuous current generation is by various forms of chemical current producers, which may be either primary or secondary in character. A simple form of cell is shown in section at Fig. 1, A, and as the action of all devices of this character is based on the same principles, it will be well to consider the method of producing electricity by the chemical action of a fluid upon a metal. The simple cell shown consists of a container which is filled with an electrolyte, which may be either an alkaline or acid solution. Immersed in the liquid are two plates of metal, one being of copper, the other zinc. A wire is attached to each plate by means of suitable screw terminals.
If the ends of the plates which are not immersed in the solution are joined together a chemical action will take place between the electrolyte and the zinc plate; in fact, any form of cell consists of dissimilar elements which are capable of conducting electricity immersed in a liquid, which will act on one of them more than the other. The chemical action of electrolyte on the zinc. liberates gas bubbles, which are charged with electricity and which deposit themselves on the copper plate. The copper element serves merely as a collecting member, and is termed the "negative” plate, while the zinc which is acted upon by the solution is termed the positive member. The flow of current is from the zinc to the copper plate through the electrolyte, and it is returned from the copper plate to the zinc element by the wiring which comprises the external circuit. The terminal on the cop
per plate is known as the “positive;" that on the zinc is called the “negative."
While in the cell shown zinc and copper are used, any other combination of metals between which there exists a difference in electrical condition when one of them is acted upon by a salt or acid may be employed. Any salt or acid solution will act as an electrolyte if it will combine chemically with one of the ele
Fig. 1.-Types of Chemical Producers. A-Elementary Primary Cell.
B—Construction of Dry Cell. C—Simple Form of Secondary Battery. D—The Lead Plate Roll and How It is Made.
ments and if it does not at the same time offer too great a resistance to the passage of the electric current. The current strength will vary with the nature of the elements used, and will have a higher value when the chemical action is more pronounced between the positive member and the electrolyte.
As the vibrations which obtain when the automobile is driven over highways makes it difficult to use primary cells in which there is a surplus of liquid, a form of cell has been devised in which the liquid electrolyte is replaced by a solid substance which cannot splash out of the container even if the cell is not carefully sealed. A current producer of this nature is depicted in section at Fig. 1, B. This is known as a dry cell, and consists of a zinc can, in the center of which a carbon rod is placed. The electrolyte is held close to the zinc or negative member by an absorbent lining of blotting paper, and the carbon rod is surrounded by some depolarizing inaterial. The top of the cell is sealed with pitch to prevent loss of depolarizer.
The depolarizer is needed that the cell may continue to generate current. When the circuit of a simple cell is completed the current generation is brisker than after the cell has been producing electricity for a time. When the cell has been in action the positive element becomes covered with bubbles of hydrogen gas, which is a poor conductor of electricity and tends to decrease the current output of the cell. To prevent these bubbles from interfering with current generation some means must be provided for disposing of the gas. In dry cells the hydrogen gas that causes polarization is combined with oxygen gas evolved by the depolarizing medium, and the combination of these two gases produces water, which does not interfere with the action of the cell. Carbon is used in a dry cell instead of copper because it is a cheaper material, and the electrolyte is a mixture of sal ammoniac and chloride of zinc, which is held in intimate contact with the zinc shell, which forms the negative element by the blotting-paper lining.
When it is desired to obtain more amperage or current quantity than could be obtained from a single cell, they are joined in series-multiple connection. With this method of wiring two or
more sets of four cells which have been joined in series are used. The zinc of one set is joined with the zinc of the other, and the two carbons are similarly connected. Any number of sets may be connected in series multiple, and the amperage of the combination is increased proportionately to the number of sets joined together in this manner.
When dry cells are connected in series, the voltage of one
Fig. 2.-Methods of Joining Dry Cells to Form Batteries of
cell is multiplied by the number of cells, and the amperage obtained from the set is equal to that of one cell. When connected in series multiple, as shown at Fig. 2, the amperage is equal to two cells, and the voltage produced is equivalent to that obtained from four cells. When twelve cells are joined in series multiple, the amperage is equal to that of one cell multiplied by three, while the voltage or current pressure is equal to that produced by one cell multiplied by the number of cells which are in series in