Which current waveform creates a constant voltage without fluctuations in polarity?

Direct current (DC) is characterized by its ability to maintain a constant voltage level over time without fluctuations in polarity. This means that in a DC circuit, the electrical current flows in a single, constant direction, and the voltage remains stable. This property makes DC particularly suitable for powering devices that require a consistent voltage, such as batteries and electronic circuits.

In contrast, alternating current (AC) changes direction periodically and varies in voltage, leading to fluctuations in both polarity and amplitude. Pulsating direct current, while it maintains a unidirectional flow, does exhibit fluctuations in voltage levels, as the current amplitude changes over time. Unrectified alternating current remains an AC signal, which naturally involves continuous changes in polarity. Therefore, the attributes of DC make it the definitive choice for a current waveform that provides a steady voltage without any fluctuations.