What term describes a conductor with a high current carrying capacity and low AC resistance?

The term that describes a conductor with a high current carrying capacity and low AC resistance is best represented by "Segmental." A segmental conductor typically consists of several conductors arranged in a way that increases the effective area for current while reducing the AC losses due to resistance. This design minimizes the skin effect, which is more significant in AC transmission, allowing for better performance at higher frequencies.

In contrast, options such as single core, composite, and flat refer to specific construction designs or materials which may not inherently provide the same level of performance as a segmental configuration when it comes to minimizing AC resistance and optimizing current carrying capacity. Therefore, the segmental design is particularly suited for applications where efficiency and performance are critical in terms of both current flow and minimizing losses.