We have seen that when a current passes through the solution of an electrolyte, chemical changes take place i.e., electrical energy is converted into chemical energy. Similarly, we can convert chemical energy into electrical energy. An electric cell is a device that converts chemical energy into electrical energy. 

An electric cell essentially consists of two different metal plates. These plates immerse in electrolyte solution. The plates are called electrodes. Due to chemical action, between plates and electrolyte one plate is maintained at positive potential and other at the negative potential. An e.m.f. is developed in cell. These plates and electrolyte is placed in a non reactive container and this assembly is called an electric cell. When load(lamp etc.) connects between two plates current start flows.

Types of Cells

Cells can be divided into two main types, (i)  Primary cells (ii) Secondary cells.

Primary Cells

A cell which produces electrical energy and after some times of working becomes inactive, is known as primary cell. In simple ways, we can say that a cell in which chemical action is not reversible is called a primary cell.

Few examples of primary cells:-

  • Valtaic cell
  • Daniel cell
  • Leclanche cell
  • Clark cell
  • Weston cell
Primary cell
Primary Cell
Pic Courtesy:- Eveready 

A primary cell supplies current until the electrolyte is exhausted or the negative plate is completely dissolved. This cell requires fresh material for becoming active again.

Secondary Cell

A cell which is used again and again after charging is called a secondary cell. In simple words, we can say that a cell in which chemical reaction is reversible is known as secondary cell. The working of primary and secondary cell is basically same but differ in the method in which it may be renewed. 

Few examples of secondary cell:-                                                           

  • Lead-acid battery
  • Nickel – cadmium cell
  • Edison cell

When secondary cell is fully charged, it delivers energy to the connected load, once it is discharged, by applying external source, energy is induced in the cell.

Applications of Secondary Cell

Secondary cell is used in various places due to its several advantages.

  • It is used in substations for operation of relays.
  • It is used in automobile vehicles.
  • It is used in laboratories.
  • It is used in domestic inverters etc.