Final answer:
Direct current (DC) is the flow of electrons in a single direction with a constant voltage, typically found in batteries and vehicle electrical systems, whereas alternating current (AC) periodically reverses direction.
Step-by-step explanation:
The continuous flow of electrons in a single direction or polarity is known as direct current (DC). Unlike alternating current (AC), direct current maintains a fixed direction and a constant voltage. This means that in direct current systems, the electric charge flows only one way. Examples of DC include the power from batteries and the electrical systems in most vehicles.
Comparatively, alternating current is the flow of electric charge that periodically reverses direction. This is the type of current that you would get from a standard household power outlet, where the current increases and decreases in a sinusoidal pattern, switching directions regularly.