What is a battery

A battery is a device for converting chemical energy into electrical energy. 

The word cell comes from the Latin for small room, which explains why a prisoner is kept in a cell.  

A battery is an electrochemical cell, and is defined as a device comprising two or more redox couples (where each couple comprises two redox states of the same material). An oxidation reaction occurs at the negative pole of the battery in tandem with a reduction reaction at the positive pole. Both reactions proceed with the passage of current. The two redox couples are separated physically by an electrolyte. 

The battery requires two redox couples because it is a cell. Each couple could be thought of as representing half of a complete cell. This sort of reasoning explains why the two redox couples are called half-cells. We could, therefore, redefine a cell as a device comprising two half-cells separated with an electrolyte. 

In practice, the voltage of a battery is measured when its two ends are connected to the two terminals of a voltmeter, one contact secured to the positive terminal of the battery and the other at the negative. But a voltmeter is a device to measure differences in potential, so we start to see how the voltage cited on a battery label is simply the difference in potential between the two poles of the battery. 

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What is a battery Describe several types of batteries. 

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