A current waveform varies periodically from zero up to a positive maximum, returns to zero, and repeats without reversing polarity. What is the correct classification of this signal?

Introduction:
Waveform terminology distinguishes DC, AC, and intermediate cases that are neither constant nor sign-reversing. Correct classification helps predict effects such as rectification outcomes and filter behavior.

Given Data / Assumptions:

• Current is always nonnegative (never below zero).
• It starts at zero, rises to a positive maximum, returns to zero, and repeats.
• The pattern is periodic.

Concept / Approach:
An alternating signal must change polarity (positive to negative and back). A direct signal is constant over time. The described waveform is periodic and unidirectional, which is the definition of a pulsating (or pulsating DC) signal often seen after rectification before filtering.

Step-by-Step Solution:
1) Check polarity: waveform never goes negative → not alternating.2) Check constancy: amplitude varies over time → not direct (not constant DC).3) Check periodicity: repeats → qualifies as pulsating.4) Conclude: the correct classification is pulsating.

Verification / Alternative check:
Half-wave or full-wave rectifier outputs are classic examples of pulsating DC: unidirectional but time-varying and periodic.

Why Other Options Are Wrong:
Direct: implies constant magnitude; contradicted by variation.Alternating: requires polarity reversal; not present.Repetitive: true but too generic; does not specify unidirectional variation.

Common Pitfalls:
Assuming any periodic waveform is alternating. Alternating specifically means sign reversal, not merely repetition.

Final Answer:
pulsating