Name: Applications of Potentiometer
Uploaded: 2019-07-19
Duration: 4 min 30 s
Description: Since potentiometers are very versatile and handy to use, it is vital to understand their working principle and applications fully. In this video, learn abou...

Question

Give a brief account of an electrochemical cell. Distinguish between a primary cell and a secondary cell. Mention the factors on which the internal resistance of a cell depends.

Accepted Answer

An electrochemical cell is a device that can generate electrical energy from the chemical reactions occurring in it, or use the electrical energy supplied to it to facilitate chemical reactions in it. These devices are capable of converting chemical energy into electrical energy, or vice versa.

A primary cell is a battery that is designed to be used once and discarded, and not recharged with electricity and reused like a secondary cell (rechargeable battery). In general, the electrochemical reaction occurring in the cell is not reversible, rendering the cell nonchargeable. As a primary cell is used, chemical reactions in the battery use up the chemicals that generate the power; when they are gone, the battery stops producing electricity. In contrast, in a secondary cell, the reaction can be reversed by running a current into the cell with a battery charger to recharge it, regenerating the chemical reactants. Primary cells are made in a range of standard sizes to power small household appliances such as flashlights and portable radios.

Differences between primary cell and secondary cells are tabulated.

Primary cell Secondary cell

1) Have high energy density and slow in discharge and easy to use. 1) They are smaller energy density.

2) There are no fluids in the cells hence it is also called as dry cells. 2) There are made up of wet cells (flooded and liquid cells) and molten salt (liquid cells with different composition).

3) It has high internal resistance. 3) It has a low internal resistance.

4) It has an irreversible chemical reaction. 4) It has a reversible chemical reaction.

5) Its design is smaller and lighter. 5) Its design is more complex and heavier.

6) Its initial cost is cheap. 6) Its initial cost is high.

The opposition offered by the electrolyte of the cell to the flow of electric current through it is called the internal resistance of the cell.
Factors affecting Internal resistance of a cell:

Larger the separation between the electrodes of the cell, more the length of the electrolyte through which current has to flow and consequently a higher value of internal resistance.

Greater the conductivity of the electrolyte, lesser is the internal resistance of the cell. That is, internal resistance depends on the nature of the electrolyte.

The internal resistance of a cell is inversely proportional to the common area of the electrodes dipping in the electrolyte.

The internal resistance of a cell depends on the nature of the electrodes.

Give a brief account of an electrochemical cell. Distinguish between a primary cell and a secondary cell. Mention the factors on which the internal resistance of a cell depends.

Important Questions on Direct Current Circuits

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