When a capillary tube has a larger diameter, the length of the capillary tube must be ______ to have the same effect as one with a smaller diameter:

A capillary tube's function is based on its ability to create a pressure drop, which is influenced by its length and diameter. When a capillary tube has a larger diameter, it can pass refrigerant more easily, resulting in a lower pressure drop for a given length of the tube. To compensate for this reduced pressure drop and achieve the same effect as a smaller diameter tube, the length of the larger diameter tube must be increased.

The longer length ensures that the refrigerant experiences sufficient resistance as it flows through the tube, allowing it to create the desired pressure drop similar to that of a smaller diameter tube. Thus, the correct answer reflects the necessary condition to maintain consistent operation in the system despite the change in diameter.