Direct current
Direct current (DC or "continuous current") is the flow of electricity in a single direction, from the negative to the positive terminals (potential, poles).
The direct current always flow in the same direction, distinguishing it from the alternating current (AC). Direct current used to be called "Galvanic current".
Batteries are some of the main sources of direct current (DC), but many other sources also exist such as bridge rectifiers in power supply, solar panels, etc.
Typically, the current goes through a conductor and other things that can carry DC. DC is also sent through a vacuum as in electron beams or ion beams.
The first commercial electric power transmission was developed by Thomas Edison in the late nineteenth century using direct current. Today nearly all electric power distribution uses alternating current because of the advantages with transformers and transmission. High-voltage direct current is often used for transporting electricity to places far away.
For applications requiring direct current, the alternating current is typically distributed to a substation and then converted to direct current.
Long after the usage of direct current had been established, physicists realized that the current was made of negative electric charges, the electrons, and that the actual flow was from the negative to the positive pole (and so-called "holes" flow in the opposite direction), but by convention, the usage of the term was never changed.
Direct Current Media
Direct current (DC) (red line). The vertical axis shows current or voltage and the horizontal 't' axis measures time and shows the zero value.
Brush Electric Company's central power plant with dynamos generating direct current to power arc lamps for public lighting in New York. Beginning operation in December 1880 at 133 West Twenty-Fifth Street, the high voltages it operated at allowed it to power a 2-mile (3.2 km) long circuit.
A diagram showing types of direct current (battery, half-wave and full wave rectification).
This symbol which can be represented with Unicode character Template:U+ (⎓) is found on many electronic devices that either require or produce direct current.
Related pages
Other websites
- AC/DC: What's the Difference?. Edison's Miracle of Light, American Experience. (PBS)