Final answer:
The exact number of steps requiring a switch at both ends for staircase lights is not provided as it varies by local building codes. In a light bulb with three power settings, a minimum of two filaments is needed, while a step-up transformer must have the number of output coils to input coils ratio of five to increase the voltage fivefold. Consult local building codes for switch requirements.
Step-by-step explanation:
The question about the requirement for lights on staircases having switches at both ends is related to building codes and safety, which typically falls under the field of engineering. This kind of question is generally applicable to high school level building trades, architecture, or engineering courses. For lights for staircases with more than a certain number of steps, the international building codes generally require a switch at both ends of the staircase. However, the exact number of steps may vary based on local codes and amendments. It is important to consult the specific building codes applicable in your area for the correct answer.
Addressing the other information provided, some light bulbs have multiple power settings, and to achieve three distinct power settings (not including off), you would need a minimum of two filaments, as you can have one filament on, the other filament on, or both filaments on simultaneously, creating three levels of light intensity. For a step-up transformer to increase the voltage fivefold, the ratio of the number of output coils to the number of input coils should be five times, since voltage increase in a transformer is directly proportional to the ratio of the number of coils.