INTRODUCTION

Current not only flows through metallic conductors but also flows though some liquids called electrolytes.¹ These liquids provide oppositely charged ions, and the conduction is due to the movement of these ions (not due to the movement of free electrons). The flow of current through electrolyte leads to chemical changes. Therefore, in this process, electrical energy is converted into chemical energy and the converse of this is also true. The chemical effect of electric current has many applications, for example, extraction of pure metals from ores, electrodeposition, electroplating, electrotyping, production of oxygen, storage batteries, and so on.

One of the major applications of chemical effect of electric current is storage batteries. Battery is the only device in which electrical energy can be stored in the form of chemical energy. The important applications of batteries are as follows:

1. In automobiles
2. Used for lighting purposes in trains
3. To operate protective devices at substations
4. At telephone exchanges
5. Used in emergency lights at hospitals, theatres, and other places

In this chapter, storage batteries are discussed in detail.