Alternating current is easier to interrupt than direct current because periodically (120 times per second in a 60Hz circuit) the current value becomes ______.

Alternating current is easier to interrupt than direct current because periodically (120 times per second in a 60Hz circuit) the current value becomes ______.

• A. Zero
• B. Maximum
• C. Constant
• D. Fluctuating

Answer: (A)

The idea being tested is that switching AC is easiest when the current momentarily goes to zero. In a 60 Hz system, the current is sinusoidal and crosses zero 120 times each second (twice per cycle). At those instants, there’s no current to sustain an arc, so opening the switch or breaker happens with much less arcing and stress on the interrupter. That’s why alternating current is easier to interrupt at zero current. If the current never reached zero, as with direct current, interrupting would have to break a continuous flow, which makes arcing more likely. So the fill is zero.

The idea being tested is that switching AC is easiest when the current momentarily goes to zero. In a 60 Hz system, the current is sinusoidal and crosses zero 120 times each second (twice per cycle). At those instants, there’s no current to sustain an arc, so opening the switch or breaker happens with much less arcing and stress on the interrupter. That’s why alternating current is easier to interrupt at zero current. If the current never reached zero, as with direct current, interrupting would have to break a continuous flow, which makes arcing more likely. So the fill is zero.