Detailed Instructions: Given a scientific passage and an answer, generate a question for the given answer.
Q: Passage: Figure 20.19 Power is distributed over large distances at high voltage to reduce power loss in the transmission lines. The voltages generated at the power plant are stepped up by passive devices called transformers (see Transformers) to 330,000 volts (or more in some places worldwide). At the point of use, the transformers reduce the voltage transmitted for safe residential and commercial use. (Credit: GeorgHH, Wikimedia Commons). Answer: transformers
A:
The voltages generated at a power plant are stepped up by what passive devices, which then reduce voltage to a safe level at the point of use?