Which description best fits alternating current?

Which description best fits alternating current?

• A. Current flows in one direction only.
• B. Voltage is constant.
• C. Current changes direction periodically.
• D. The circuit is always closed.

Answer: (C)

Alternating current is defined by a current that reverses direction over time. This happens because the supply voltage periodically reverses polarity (such as at 50 or 60 Hz), so the flow of charge switches direction with each half-cycle. That periodic reversal is the essence of AC, unlike direct current, which flows in one fixed direction. The voltage in AC also varies with time rather than staying constant, and a circuit being closed or open is a separate condition that isn’t what distinguishes AC.

Alternating current is defined by a current that reverses direction over time. This happens because the supply voltage periodically reverses polarity (such as at 50 or 60 Hz), so the flow of charge switches direction with each half-cycle. That periodic reversal is the essence of AC, unlike direct current, which flows in one fixed direction. The voltage in AC also varies with time rather than staying constant, and a circuit being closed or open is a separate condition that isn’t what distinguishes AC.