Alternating current is easier to interrupt than direct current because the current value periodically becomes __________.

The correct answer is zero, which is significant in understanding the nature of alternating current (AC). One of the key characteristics of AC is that it periodically reverses direction, resulting in the current flowing back and forth. As it oscillates, the current's value crosses zero at specific intervals, which allows for easier interruption of the flow.

When current is at zero, there is no electrical flow at that instant, making it much simpler for circuit breakers and other protective devices to halt the current without arcing (which is more likely to occur at higher values of direct current). In contrast, direct current (DC) flows continuously in one direction and does not naturally reach zero, leading to a greater risk of maintained electrical arcs when attempting to interrupt the supply. This attribute of AC is particularly advantageous in power systems, where reliable interruption is crucial for safety and equipment protection.