Direct Current


Definition of Direct Current

Direct current (DC) is an electrical current that flows in only one direction. Not to be confused with alternating current (AC), which switches direction back and forth, at regular intervals.

In more familiar terms, DC is the type of electric current found in low voltage applications, such as LEDs, battery-powered devices, solar-powered batteries and smaller boats because DC is easier to control and allows electrical circuits to be compact.

AC is the type of current in the mains power supply, which is basically the utility power delivered to homes and commercial buildings.

However, big appliances such as washing machines, and large recreational boats, such as motor yachts use a combination of AC and DC.

Direct current has a few distinct characteristics which include:

  • Unidirectional flow: DC flows in only one direction, making it useful for powering devices that require a steady and consistent voltage, such as paralleled LED strip lights
  • Energy efficiency: DC systems are generally more energy efficient than AC systems, as there is no energy loss due to reactance.
  • Battery powered: DC is commonly used in battery-powered devices and circuits, as it works well for compact circuits.
  • Limited distance: DC power transmission is limited in distance due to voltage drop over long distances
  • Fixed polarity: The positive and negative terminals of the power source don’t switch. Power flows from the positive to the negative terminals.

Understanding the type of current and voltage your devices or light fixtures use is essential to ensure effectiveness and prevent damage.

Most boats have a DC voltage of 12 V or 24 V. If you had the Slim AC LED Flood Light 30W, for example, it wouldn’t be compatible with the boat’s power supply. Instead it would be better suited as a dock light where line voltage is available.

Example of Direct Current in a Sentence

"The LED boat lights operate on direct current, supplied by the boat's battery."

Synonyms: continuous current, polarized current

Related Terms for Direct Current