Direct Current And Its Applications

Direct current is the unidirectional flow of electrons from an area of negative charge to an area of positive charge through a conductor. A direct current always flows in one direction as it flows from one point to another. A DC voltage is always positive or it is always negative. DC voltage has a fixed polarity and the magnitude of the current is constant. It may increase or decrease in intensity but constant in amplitude. The flow of electric current originates from the positive terminal towards the negative terminal. The direction of the electron flow is from the negative terminal of the battery to the positive terminal. The graphical representation of a DC voltage is a straight line across the time-line with a constant voltage level.

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Definition Of DC

A DC refers to a voltage with a single polarity of voltage or current. It also refers to constant, zero frequency, or slowly moving mean value of a voltage or current. The voltage across a DC voltage source is constant as is the current through a DC current source. Direct current in an electric circuit has constant voltage and constant current. A stationary voltage or current has a DC component and a zero time varying component. 

Sources of DC

The sources of direct current are batteries, thermocouples, solar cells, capacitive storage etc. Fuel cells also produce DC by mixing hydrogen and oxygen with a catalyst, producing DC electricity and water as byproduct. Direct current may also be obtained by rectification and filtration of an alternating current or AC from a generator, which is a pulsating DC. The direct current can flow through a conductor such as electrical wires and cables. DC can also flow through semiconductors, insulators, or even through vacuum.

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Most electronic circuits require a direct current that is steady and constant in amplitude for their smooth functioning. Some circuits such as lamps, heaters, and some type of motors may work with a pulsating DC.

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DC Applications
Direct current is used for powering most electronic devices, charge batteries, run motors etc.  It is also commercially used in the production of aluminum and other metals, separation of metals, electroplating, and other electrochemical processes. Telephones are connected to wires that carry DC for their functioning and telephone exchanges have communication equipment that works on direct current. Direct current is used in driving electrical vehicles such as electric cars, bikes, carts, trams, rail etc.  High voltage direct current is used to transmit electricity from the generator site to the place where it is used and to interconnect intermittent power grids.