Electric current

Direct current

Direct current

The direct current is a type of electric current very important in solar energy where the direction of flow of electric charges (electrons) does not vary. In many devices the symbol to indicate direct current is DC (direct current), or using the symbol of a continuous line (-) flanked by three shorter lines (---), for the alternating current that is used instead of AC (alternating current) or the symbol (~).

The flow of charges occurs through a conductor, such as a metallic thread. The flow could also be established through a semiconductor, an insulator or even vacuum as in a cathode ray tube. In this type of electric current (direct current) the electric charges always flow in the same direction, being a characteristic feature in front of the alternating current.

A deduced synonym of direct current is galvanic current.

The first commercial electricity network, developed by Thomas Edison at the end of the 19th century, used direct current. Nowadays, due to the advantages of alternating current in terms of transformation and transport possibilities, the transport and distribution networks use almost exclusively alternating current. In the case of applications that need direct current, as in the case of rail using the third rail system, the alternating current arrives at a substation that uses a rectifier to convert it into direct current.

Production and conversion of direct current

Direct current and other types of current The direct current can be produced not only with a dynamo, but also through an alternator and then from an alternating current (AC) with, followed by a straightening process, made with diodes or bridges rectifiers. Actually, these devices eliminate the negative component of the alternating current, producing a current that is not continuous but pulsating unidirectional, that is, ideally composed of an alternating current superimposed on a continuous one. A capacitor next to the rectifier allows to level the signal, supplying a current as close as possible to a continuous value.

Conversely, the conversion of a direct current into an alternating current is much more complex, in particular because it is necessary to generate information about the waveform, the frequency and the phase. The operation is carried out by complex electronic devices called inverters.

Applications of direct current

Direct current is normally used for applications where we need a low voltage, especially where the energy is produced by batteries or by photovoltaic solar energy systems ( photovoltaic cells), since both only produce direct current.

To a circuit with direct current, it is important not to change the polarity, unless the device has a diode that allows it (most devices do not allow it).

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Last review: April 13, 2017