 - See also Ohm's Law.
DC (direct current) is the unidirectional flow or
movement of electric charge carriers (which are usually electrons).
The intensity of the current can vary with
time, but the general direction of movement stays the same at all times. As an
adjective, the term DC is used in reference to voltage
whose polarity never reverses.
In a DC circuit, electrons emerge from the negative, or minus, pole and
move towards the positive, or plus, pole. Nevertheless, physicists define DC as
traveling from plus to minus.
Direct current is produced by electrochemical and photovoltaic cells and
batteries. In contrast, the electricity available from utility mains in most
countries is AC (alternating current). Utility AC can be converted to DC by means of a power supply consisting of a
transformer, a rectifier (which prevents the flow of current from reversing), and a filter
(which eliminates current pulsations in the output of the rectifier).
Virtually all electronic and computer hardware needs DC to function.
Most solid-state equipment requires between 1.5 and 13.5 volts. Current
demands can range from practically zero for an electronic wristwatch to more than 100
amperes for a radio communications power amplifier. Equipment using vacuum tubes,
such as a high-power radio or television broadcast transmitter or a CRT (cathode-ray tube) display, require from about 150 volts to several thousand volts DC.
| LAST UPDATED: |
24 May 2005
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