What does X indicate in wire classification?

• A. Wire coated with synthetic flame retardant insulation
• B. Nylon-coated for oil resistance
• C. Copper core with no insulation
• D. High-voltage rating

Answer: (A)

The symbol X on wire classifications identifies the insulation as being a synthetic polymer with flame-retardant properties. In this coding, X signals that the conductor is coated with a synthetic, flame-resistant insulation rather than a natural or simple coating. This matters for fire safety and electrical protection, especially in environments where fire risk is a concern.

Why the other interpretations don’t fit: nylon coating for oil resistance would indicate a different designation tied to nylon or oil resistance features, not the X code. A copper core with no insulation would be bare conductor, which wouldn’t carry an insulation-related letter marking. A high-voltage rating is shown through voltage-specific markings or classifications, not simply by the letter X on insulation.