Which current waveform creates constant voltage without fluctuation in polarity?

The correct answer is Direct Current (DC) because it provides a steady, unidirectional flow of electric charge, resulting in a constant voltage that does not fluctuate in polarity. In DC, the voltage remains constant over time, which is crucial for applications such as powering certain types of medical imaging equipment, where stable voltage is necessary for consistent image quality.

In contrast, unrectified alternating current (AC) regularly changes its polarity and amplitude, leading to fluctuations in voltage levels. Half-wave rectified AC allows current to flow in one direction half of the time and cuts off the other half, resulting in a pulsed output rather than a constant voltage. Full-wave rectified AC, while more efficient than half-wave, still involves alternating positive and negative cycles, producing varying voltage levels rather than a stable output. This makes DC uniquely suited for situations requiring reliable and steady voltage.