Which of the following signifies that the conductors are a phase 3 supply?

The designation of a phase 3 supply is specifically represented by three connected conductors. In a three-phase electrical system, three conductors are utilized to distribute power, and they are typically spaced 120 degrees apart in terms of their phase angles. This configuration allows for a balanced load distribution and more efficient power delivery compared to single-phase systems.

When considering the other options, two connected conductors would typically indicate a single-phase supply, where power is carried through one conductor and returns via another. Four connected conductors could indicate a three-phase supply with a neutral wire, while five connected conductors would typically suggest a more complex system, potentially involving two separate sets of three-phase wiring along with additional conductors for other purposes such as control or grounding.

In summary, the presence of three connected conductors is the hallmark of a phase 3 supply, which facilitates efficient multi-phase power systems, making the correct answer clear.