Pulsating direct current is defined as which of the following?

• A. A current that moves in one direction but varies in intensity at regular intervals.
• B. A current that changes direction and intensity at regular intervals.
• C. A constant current.
• D. A current with zero amplitude.

Answer: (A)

Pulsating direct current is a flow that keeps its direction in the same way a DC current does, but its magnitude rises and falls in a regular ripple. This happens when AC is converted to DC (for example, with a rectifier) and there isn’t enough smoothing to flatten the peaks and valleys. So the current moves in one direction, yet its intensity varies periodically, which matches the described option.

In contrast, a current that changes direction and intensity at regular intervals is alternating current with ripple; a constant current would be steady DC with no ripple; and a current with zero amplitude is simply no current at all.