Plug fuses are never permitted in circuits that exceed what voltage between conductors?

The correct answer is based on electrical safety codes and standards that regulate the types of fuses that can be used in different voltage applications. Plug fuses are typically designed for lower voltage applications, and using them in circuits that exceed 125 volts can pose significant safety risks.

At voltages higher than 125 volts, the potential for electrical arcing and failure increases, making plug fuses inappropriate for those circuits. This is due to the design and construction of plug fuses, which may not effectively interrupt high voltage currents, thus leading to the risk of equipment damage or electrical fires.

By adhering to the regulation that plug fuses should not be used in circuits exceeding 125 volts, electrical professionals help ensure the safety and reliability of electrical systems.