Direct current (DC) is defined as?

• A. Constant
• B. Alternating direction
• C. Pulsed in bursts
• D. Variable amplitude

Answer: (A)

Direct current means current that flows in one direction. In its simplest form, that current also stays the same in magnitude over time, so there is no rising and falling of the amount of current. This unidirectional, steady flow is what distinguishes DC from alternating current, which periodically reverses direction.

The other descriptions describe different waveform features: alternating direction describes AC, and variable amplitude would mean the current changes in strength over time. Pulsed in bursts is a non-continuous form where the current may be on and off, which can still be unidirectional but is not strictly constant in magnitude. So the best match for the common definition of DC is a constant flow in one direction.