# Bright Hub Engineering

## How Is Voltage Produced?

written by: Raunekk • edited by: KennethSleight • updated: 9/27/2009

What's the most basic way of generating electricity? How was voltage generated before all the complex ways of generating electricity were developed? Find out the answers in the article inside.

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### Introduction

Looking at all the electricity that runs various equipments in our daily life, we all must have thought at some point of time as to where this electricity comes from? All of us have learned about the generators that produce loads of electricity using fuel or other sources of energy. But thinking beyond that, when and how did the electricity or voltage came to notice for the very first time? In this article we will be discussing about some of the basic ways of generating voltage.

Every one of us has heard about the charge that is produced when an iron rod is rubbed against fur. The charge is produced because of the transfer of electrons from fur to the rod, caused due to friction. As the rod receives the electrons, it becomes negative while the fur becomes positive. This transfer of charge generates an electrical potential difference which is capable of doing work. In order to procure useful work, there must be a continuous flow of potential. This means that if one electron leaves the negative side, there must be an electron ready to take its place.

Let’s take a look at the basic methods that are used to produce a voltage.

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### Voltage by Friction

This method of generating voltage is not widely used to produce work. As discussed earlier, voltage can be generated by friction by rubbing an iron rod against fur. Due to the nature of the materials used in this method voltage cannot be generated conveniently and thus the method is not very practical. Moreover, the voltage produced is of very low magnitude, thus cannot be put to use.

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### Voltage by Pressure

One method of generating voltage is by exerting pressure on the crystals of some special materials such as quartz and tourmaline. The voltage is generated due to the specific molecular arrangement of the materials. When stress is applied to the surface of this material, two opposite polarity charges are produced on the opposite ends of the crystal. If force is exerted on the opposite side and the crystal is stretched at the same time, the charges will again appear at the ends but with reversed polarity. In this way mechanical energy is converted into electrical energy by means of pressure. This is known as piezoelectric effect. However, this method is not beneficial for generating voltage of high magnitude and thus is not used widely.

One interesting thing to note about these crystals is that they can also convert an electrical energy into mechanical energy. This means that if voltage is applied to the surface, the crystal will expand or contract according to the measure of voltage.

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### Voltage by Heat

Voltage production from heat is one of the most ancient methods of all times. All most all metals with their peculiar qualities are used to generate electricity. For e.g. copper when heated at one end, its electrons move from the hot end to the cold end. However, for iron the negative charge moves from hot end to the cold end. If a junction is created between both these metals, a transfer of electrons takes place between them, producing a potential charge. This junction is a device which is referred to as thermocouple. Thermocouples are generally used to generate energy due to difference in temperature of two different metals.

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### Image Credits

Naval Electrical Engineering Training series - Integrated Publishing Website