A dry cell is an electrochemical cell with a pasty low moisture electrolyte There are two kinds of dry cells, leclanche cell and alkaline cell.
The leclanche cell also known as the zinc carbon cell was first assembled in a porous pot. The positive electrode consists of manganese dioxide with a little carbon mixed in and the negative electrode consists of a zinc rod. The electrolyte is a solution of ammonium chloride. The way in which the cell works to produce electricity begins when the atoms of zinc at the surface of the anode gets oxidized by losing two electrons. It then becomes an ion with a positive charge. The oxidized zinc ions move away from the anode which gains an excess of electrons from the zinc atom and becomes more negatively charged than the cathode. The zinc anode's excess electrons then flow through the circuit to the carbon rod.
This movement of electrons forms an electric current when the electrons combine with manganese dioxide and water. As these substances gain these electrons and react with one another, they produce manganese oxide and negative hydroxide ions. These negative hydroxide ions then combine with positive NH3 ions that from when NH4cl is dissolved in water.
ZN + 2MnO2 + 2NH4CL Ã ZNCL2 + Mn2O3 + 2NH3 + H2OThese chemical reactions by which a carbon-zinc cell produces electricity will continue until the manganese dioxide wears away. After the cathode is used up, the cell will no longer provide anymore electricity.
The e.m.f of this cell is about 1.5 volts which in today's terms only provide very minimal electricity. It was used mostly for telegraphy, signaling and electric bell work. A carbon-zinc battery cannot be recharged efficiently, quite heavy and also prone to breakage, however when used the battery only requires very little...