Which type of current flows in one direction only?

Direct current, or DC, flows in one direction only, making it distinct from other types of current. In a DC circuit, charges move steadily along a single path, ensuring a consistent polarity—meaning the voltage remains constant in relation to time. This unidirectional flow is typical in batteries and many electronic devices.

In contrast, alternating current, which is also very common, periodically reverses direction, cycling from positive to negative. Pulsating current and ripple current, while they may have directional characteristics, indicate variations in the flow that involve changes over time rather than a steady, unidirectional flow like in direct current. Thus, the characteristic of direct current as having a consistent and uniform direction confirms its definition and sets it apart from the other types of current mentioned.