Cells and Batteries

4 Cells and Batteries

4.0 Introduction

Cells and batteries are portable sources of electrical energy. They are used in areas where a normal electrical supply is not available. Generally, in the rural areas, people use dry cells for their torches. Cells are of two types, the primary cell and the secondary cell.

Due to advancement in technology looking at cell does not guarantee it is primary or secondary but rather evaluating if it rechargeable or not gives a precise answer.  Therefore torch dry cells belong to the primary cells if they are not rechargeable; while the car battery is made up of secondary cells.

Secondary cells are more expensive than primary cells, but they last longer. Therefore, they are used in very remote areas for special jobs such as in cellphones, mobile radio transmitters and telephone exchanges.

When two or more cells are connected together, they form a battery. A battery is, therefore, capable of producing more electrical energy than a single cell.

Batteries are used in hospitals, laboratories and many other places to operate standby generators for providing emergency power where an electrical source of energy is essential at all times. In such places, they are called backup supplies.

Their uses come handy when normal electrical supply fails. 

4.1 Electric Cell

A cell comprises an arrangement of chemically active materials whose reaction produces electric energy when the external electric circuit is completed.

Basic parts of an electric cell are:

(a)        a positive electrode (anode),

(b)        a negative electrode (cathode),

(c)        an electrolyte (active reagent).

The electrolyte reacts with either one or both electrodes to produce electric energy. Reaction stops when the electric circuit is opened.

There are two types of cells:

Primary Cells

Secondary Cells

These are rechargeable. After they are depleted, they can be recharged by connecting them to a battery charger. In the process, a current is passed into the cell in the reverse direction. This reverses the chemical reaction.