New York State Master Electrician Practice Exam

Glass or porcelain knobs are commonly used to support open conductors because they provide effective insulation and can withstand high temperatures without deforming. These materials are non-conductive and are specifically designed to minimize the risk of short circuits or electrical shocks, ensuring that the conductors are securely held in place while maintaining safety standards.

The use of these insulating materials aligns with electrical codes and safety regulations, which prioritize the prevention of electrical hazards. While plastic insulators and wooden knobs may also serve as supports for conductors, they may not have the same level of durability or heat resistance as glass or porcelain options. Metal brackets, on the other hand, are conductive and would not be appropriate for supporting open conductors as they could introduce significant safety risks if they come into contact with the conductors. Therefore, glass or porcelain knobs are the most suitable choice for safely supporting open conductors in accordance with safety standards.