Corriente Dc

Direct current 1
Direct current
Direct current (DC) is the unidirectional flow of electric charge. Direct current is produced by such sources as
batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may
flow in a conductor such as a wire, but can also be through semiconductors, insulators, or even through a vacuum as
in electron orion beams. The electric charge flows in a constant direction, distinguishing it from alternating current
(AC). A term formerly used for direct current was galvanic current.[1]
Types of direct current.
Direct current may be obtained from an alternating
current supply by use of a current-switching
arrangement called a rectifier, which contains
electronic elements (usually) or electromechanicalelements (historically) that allow current to flow only
in one direction. Direct current may be made into
alternating current with an inverter or a
motor-generator set.
The first commercial electric power transmission
(developed by Thomas Edison in the late nineteenth
century) used direct current. Because of significant
historical advantages of alternating current over direct
current intransforming and transmission, electric
power distribution was nearly all alternating current
until a few years ago. In the mid 1950s, HVDC
transmission was developed, which is now replacing
the older high voltage alternating current systems. For applications requiring direct current, such as third rail power
systems, alternating current is distributed to a substation, which utilizes arectifier to convert the power to direct
current. See War of Currents.
Direct current is used to charge batteries, and in nearly all electronic systems as the power supply. Very large
quantities of direct-current power are used in production of aluminum and other electrochemical processes. Direct
current is used for some railway propulsion, especially in urban areas. High voltage direct current isused to transmit
large amounts of power from remote generation sites or to interconnect alternating current power grids.
Various definitions
Within electrical engineering, the term DC is used to refer to power systems that use only one polarity of voltage or
current, and to refer to the constant, zero-frequency, or slowly varying local mean value of a voltage or current.[2]
For example, thevoltage across a DC voltage source is constant as is the current through a DC current source. The
DC solution of an electric circuit is the solution where all voltages and currents are constant. It can be shown that
any stationary voltage or current waveform can be decomposed into a sum of a DC component and a zero-mean
time-varying component; the DC component is defined to be the expected value,or the average value of the voltage
or current over all time.
Although DC stands for "direct current", DC often refers to "constant polarity". Under this definition, DC voltages
can vary in time, as seen in the raw output of a rectifier or the fluctuating voice signal on a telephone line.
Some forms of DC (such as that produced by a voltage regulator) have almost no variations in voltage, butmay still
have variations in output power and current.
Direct current 2
Applications
Direct-current installations usually have different types of sockets, switches, and fixtures, mostly due to the low
voltages used, from those suitable for alternating current. It is usually important with a direct-current appliance not to
reverse polarity unless the device has a diode bridge to correct forthis (most battery-powered devices do not).
This symbol is found on many electronic devices that
either require or produce direct current.
DC is commonly found in many low-voltage applications,
especially where these are powered by batteries, which can
produce only DC, or solar power systems, since solar cells can
produce only DC. Most automotive applications use DC, although
the alternator...