What is the maximum duration that a circuit can operate to be classified as intermittent duty?

A circuit is classified as intermittent duty when it operates for a specific period followed by an off period, allowing for cooling or reset time. The correct answer identifies this duration as two minutes. In many electrical standards, circuits categorized under intermittent duty can operate up to two minutes continuously before needing a rest period. This classification helps in determining the thermal limits and proper cooling methods required for equipment, ensuring safety and reliability during operation.

The reason the other durations are not correct is that they either fall outside the accepted operational time limits for intermittent duty or could potentially classify the circuit under a different duty cycle. For example, one minute may be too short for many applications, while durations greater than two minutes typically suggest a different operational capacity, such as short-time duty or continuous operation, which have different thermal and load considerations.