Final answer:
The neutral conductor must be sized to carry the maximum unbalanced current, not the maximum available ground-fault current. Thus, the correct option is 'a. I only'. Proper sizing is crucial for safety and functionality in electrical systems.
Explanation:
Determining the Sizing of a Neutral Conductor
In electrical engineering, the sizing of the neutral conductor is critical for ensuring safety and functionality in electrical systems. The question asks whether the neutral conductor must be sized to carry: I. the maximum unbalanced current and II. the maximum available ground-fault current.
Understanding the Requirements
The neutral conductor should primarily be sized to carry the maximum unbalanced current. This is defined as the current that can flow through the neutral conductor when there is a difference in the current between the live conductors and is essential for safe operation. In contrast, the neutral does not need to be sized to handle maximum available ground-fault current since the ground-fault protection mechanisms are designed to handle such faults without needing to place this burden on the neutral.
Conclusion
Therefore, the correct answer to the question is a. I only. By sizing the neutral conductor to handle the maximum unbalanced current, we ensure that it operates safely and efficiently under normal conditions.
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