Читать книгу Lessons in Wireless Telegraphy онлайн

11 страница из 17

FIG. 10. Storage Cells.

What is effected in the storage cell is really the storage of chemical energy and not the storage of electricity, for, properly speaking, the energy is put into the form of chemical affinity and there is in reality no more electricity actually in the cell at the end of a charge than there is when the cell is discharged.

The storage battery is the most convenient means of absorbing electrical energy at one time or place and using it at another time or place.

Storage cells are very often employed in wireless stations for emergency purposes so that in case the dynamo supplying current fails the station will not be thrown out of operation.

The voltage of a storage cell is about two volts.

ssss1

The Units of Measurement. Direct and Alternating Currents. Ohm’s Law.

Electric Currents may be divided into two classes known as direct and alternating current. Either one may be measured or qualified by two electrical units called the Ampere and the Volt. The volt may be explained by likening it to the "unit of pressure" of the current, while the ampere measures the unit rate of current flow. For example, in the case of water the voltage corresponds to the pressure in pounds while the amperage would indicate the rate of water flowing.