Simple Method of producing electricity - Construction of the old dry cell model

Simple Method of Producing Electricity

Current may be produced in cells known as batteries, or it may be produced by cutting the magnetic lines of force between opposite poles of a magnet. The first method is chemical and was discovered by Volta in 1800.  A jar filled with dilute sulfuric acid into which we place a strip of zinc and a strip of copper, the two strips being connected by a copper wire.

A chemical reaction takes place and a current is set up which flows through the wire in the direction from the copper to the zinc. If the terminals of an electric bell or a small electric lamp are interposed between two parts of this wire, the bell will ring or the light will light.

 The poles of a battery are called the electrodes copper being the positive electrode and zinc being the negative electrode. The battery just described is also known as a wet cell battery. A dry cell battery works on the same principle although different chemicals are used.

By hooking up several dry cell batteries, the positive pole of one connecting with the negative pole of the next one, and so on in a series, we can develop more and more electromotive force, since the total voltage will be the sum total of the separate voltages developed by each individual battery.

Construction of the old dry cell model

Dry cells are used almost exclusively in common electrical devices such as bells, flashlights, signal devices, etc. The negative pole is the outside zinc can which serves as a containing vessel. The positive pole is a cylinder of carbon or a carbon rod.

Instead of sulfuric acid being used to develop the current between the zinc and the carbon, the space between the zinc and the carbon is filled with granulated carbon and manganese dioxide soaked in ammonium chloride.

These chemicals react to set up an electric current that flows from the positive carbon pole to the outside of the zinc which acts as the negative pole. The cell is sealed with pitch at eh top and contains cardboard and blotting paper around the sides, which reinforces it and makes a compact unit.

In some cells, copper is substituted for carbon, as you will see if you examine a flashlight battery. When the cell is put into the flashlight holder the small electric bulb is in contact with the outside zinc. By pressing a small lever at the top of the casing of the flashlight, the zinc of the cell contact with the bulb. The bulb is therefore brought in contact with both copper and zinc, the circuit is closed, and the bulb lights.