Alternating current is characterized by which description?

• A. Constant in one direction
• B. Going up and down in magnitude
• C. Pulsed with gaps
• D. Alternating at home plug frequency

Answer: (B)

Alternating current is defined by a waveform that changes over time, so the current does not flow in a single direction or stay constant. It reverses direction periodically and the amount of current—its magnitude—rises and falls in a cycle. This time-varying magnitude is the hallmark of AC, typically following a sinusoidal shape at a standard frequency like 50 or 60 Hz. That’s why describing it as going up and down in magnitude best captures what AC does.

The other descriptions don’t fit as well. Constant in one direction describes direct current, which never reverses. Pulsed with gaps describes a waveform with off intervals, not a continuous alternating signal. Alternating at home plug frequency is a real-world example, but it’s a specific frequency rather than a defining characteristic of AC itself.