Principle of primary cells

Principle of primary cells

Batt is two or more electrochemical cell.
Batt is a device to convert chemical energy into electrical energy.
Batt characteristic may vary due to many factors like internal chemistry, temperature and current drain.
There are 2 types of batt: primary and secondary. Primary batt is design to used once only and cannot be rechargeable. Secondary batt are rechargeable becoz their chemical reaction can be reversed.

Primary Cells

Ex:of primary cell is carbon-zinc battery.

primary cell : carbon-zinc












Zn plate form -ve electrode and Carbon Rod form +ve electrode.
+ve electrode is also called anode and -ve electrode is called cathode.
Solution of Ammonium chloride form the electrolyte.
As soon as the Zn plate immersed in the electrolyte, Zn atom which carries +ve ions go into the solution. This make the Zn plate becomes more -ve.
Ammonium chloride in electrolyte separate into +ve Hydrogen ions and a combination of Ammonium and chlorine which -vely charged.
When the electrodes are connected by external connection, the electrons flow from Zn plate to Carbon Rod.
These electrons will react with H+ ions and become neutral.
-vely charged ammonium and chlorine combine with the ions Zn++.

The effect of the chemical action is to remove electrons from carbon rod and to liberate free electrons at Zn plate.This will results in continuous supply of electrons available at Zn plate(-).
As there are more H atoms at the carbon rod, POLARIZATION will occur.

POLARIZATION occurs when hydrogen bubbles accumulate at the carbon rod thus insulate it from the solution. This will prevent the current to flow.
Practically, a method of DEPOLIRAZATION is employed. This is done by adding a compound called manganese dioxide.