Which material is NOT a common outdoor insulator material?

• A. Steel
• B. Porcelain
• C. Glass
• D. Polymer housing around fiberglass core

Answer: (A)

Outdoor insulators are made from dielectric materials that resist current and stand up to the weather. Steel is a conductor, so it cannot function as an insulating material; using steel would create a conductive path and defeat insulation under high voltage and moisture. Porcelain and glass are traditional insulator ceramics known for high resistivity and surfaces that shed water, reducing leakage. Modern outdoor insulators often use polymer housings around fiberglass cores, combining lightweight design with good insulation and weather resistance. Because steel conducts electricity, it is not used as a common outdoor insulator material.