Direct current (DC) is very simple, there is a positive pole and a negative pole. Between them is a voltage and that's already DC. DC is used wherever electrical energy is not needed in large quantities or has no long distances to travel. Almost all electrical components need and work internally with DC only, they have power supplies to convert from conventional AC to DC power. In cars, we have a DC voltage of 12V for the power grid that provided power to the radio, light and other comfort modules. Electric cars also have a 400V high-voltage network for example, the motor.