Читать книгу Lessons in Wireless Telegraphy онлайн

10 страница из 17

The cells so far described are all of the type known as primary cells.

SECONDARY CELLS.

The storage cell or secondary cell is made up of plates of lead, or an alloy of lead, cast in the form of a grid or framework of bars. The spaces formed in the plate by the little bars are filled with a paste of lead oxide. The paste for the positive plates are made of red lead while litharge is used for the negatives.

FIG. 9. A Storage Battery Grid.

The positive and negative plates are placed alternately in a bundle with a wooden or rubber separator between, there always being one more negative plate than positive. The negative plates are all connected in parallel at one end of the cell by means of lead connecting strips. The positive plates are connected at the other end. The plates are placed in a jar, usually glass or hard rubber, and covered with a dilute sulphuric acid solution.

The storage cell is then connected to a dynamo, the positive pole of the cell being connected to the positive pole of the dynamo and the current allowed to flow through until the plates are formed, that is to say, until the paste in the positive changes to peroxide of lead and that in the negative to spongy lead. When the cell is disconnected it will give out a current of its own lasting until it becomes discharged. The charging and discharging must be repeated several times before the cell really becomes efficient.