Direct Current (DC)
Direct current is produced when electrons flow constantly in one direction. It's abbreviated as "DC". Since direct current flows in one direction only, its electrical pressure or voltage is always oriented in one direction, or "polarity".
Interestingly, the first commercial electrical systems set up by Thomas Edison and others were direct current systems. But, for economic reasons, these were later changed to alternating current or AC systems, and are described in the Alternating Current section of this program. Today, batteries, solar panels, fuel cells and special DC generators such as wind turbines produce direct current.