Fig. 66. Chloride of Silver Cell
[View full size illustration.]

A cross-section of one form of the cell is shown in Fig. 66. Its elements are a rod of chemically-pure zinc and a rod of chloride of silver immersed in a water solution of sal ammoniac. As ordinarily constructed, the glass jar or tube is usually about 2-1/2 inches long by 1 inch in diameter. After the solution is poured in and the elements are in place the glass tube is hermetically sealed with a plug of paraffin wax.

The e.m.f. of a cell of this type is 1.03 volts and the external resistance varies with the age of the cell, being about 4 ohms at first. Care should be taken not to short-circuit these cells, or use them in any but high-resistance circuits, as they have but little energy and become quickly exhausted if compelled to work in low-resistance circuits.

Conventional Symbol. The conventional symbol for a cell, either of the primary or the secondary type, consists of a long thin line and a short heavy line side by side and parallel. A battery is represented by a number of pairs of such lines, as in Fig. 67. The two lines of each pair are supposed to represent the two electrodes of a cell. Where any significance is to be placed on the polarity of the cell or battery the long thin line is supposed to represent the positively charged plate and the short thick line the negatively charged plate. The number of pairs may indicate the number of cells in the battery. Frequently, however, a few pairs of such lines are employed merely for the purpose of indicating a battery without regard to its polarity or its number of cells.

Fig. 67. Battery Symbols
[View full size illustration.]

In Fig. 67 the representation at A is that of a battery of a number of cells connected in parallel; that at B of a battery with the cells connected in series; and that at C of a battery with one of its poles grounded.

[ToC]