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How arises electrical voltage?

Voltage supply can occur in many different ways. The main reason why voltage may occur is by the energy that comes from different sources.

By magnetic and mechanical action
In a copper-wire that moves between the poles of a magnet, there will be created voltage. For example, magnetic energy is converted to electrical energy. Such rotating (moving) sources is called generators. So you have: the alternator that supplies DC, bicycle magneto that AC supplies and alternators from cars and power plants that supplies three phase voltage.

This principle was discovered by the British physicist Faraday around 1830. He also discovered the 'Faraday cage'.

Example
The dynamo of a bicycle. If you place the wheel of the dynamo against the tire and you turn the wheel of the bicycle then there arise voltage in the magneto and that provides power to the bicycle lamps that can now can give light.

Heat operation
Two different metals, for example iron and constantan, are welded to each other on one side. By the heating of the weld there will be formed a small voltage between the two metals.

Here takes the conversion of thermal energy into electrical energy place.

The sources are called thermocouples or thermoelectric elements. They are not interesting enough for the production of electrical energy but are uses as temperature sensors. Whit this technique are big temperatures measured in furnaces with high temperatures. They ar also useful as control technology in gas heaters. Suppose that the pilot light is off, than the voltage disappears. This let the electromagnetism disappear, allowing the throttle to be idle and the gas shuts off.

Example
Burn a candle and hold a thermocouple above the flame. At the free ends you connect and millivolt meter and you heat the contact point. The mV-meter gives a few milli-volts.

By lighting effect
The rays of the sun can be converted to solar-energy. The light energy is converted by the photovoltaic cells or solar cells in electrical energy. They can be found in solar panels on roofs, in aerospace, in measurement and control techniques, watches, calculators, ...

By chemical action
Between two different metals, take copper and zinc, immersed in a salt or acid solution, arises a DC voltage. A chemical energy is converted to electrical energy. So, it becomes possible to generate electrical energy, in a limited small amount.

This principle was discovered by the Italian scholar Volta around the year 1800.

Example
Insert a stick a stick of copper and a stick of zinc in a lemon. The two sticks may not touch each other. Now connect each stick with a line of a DC volt meter. So the needle goes about 1 volt. If it doesn't then you should swap the two lines.

Transposition of energy by electricity
By chemical, mechanical, thermal or light effect a tension, so you get an electrical source. This voltage may cause an electrical current, which can be turned again in to a chemical, mechanical, thermal or light-function.

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