Final answer:
The depth of screened sand under conductors in an underground branch circuit installation may vary, with modern practices suggesting as much as 15 diameters deep based on the size of the conduit or cable. In electrical power distribution, superconducting wires do not dissipate power compared to copper wires.
Step-by-step explanation:
When dealing with an underground branch circuit installation, there are specific requirements for the depth of screened sand beneath the conductors to ensure protection and durability of the electrical system. The depth can vary depending on multiple factors such as the type of installation, local code requirements, and the kind of conductors used. A former rule of thumb was to have 7-8 inches deep of screened sand under the conductors, but modern practices and some codes may call for as much as 15 diameters deep of the conduit or cable used.
In terms of electrical power distribution, like that from a power plant, the efficiency of transmission materials can make a significant difference in energy loss. Copper wires, for instance, dissipate more power due to resistance when compared with superconducting wires, which have no electrical resistance and thus do not dissipate any power.