Wiring and componentsQuestion 811 of 1506

The letters in a conductor type code such as THWN mostly describe which part of the conductor?

The number of strands in the copper
The voltage drop per metre
The colour of the neutral conductor
The insulation and its properties

Show answer

Correct answer: The insulation and its properties

The letters are mostly abbreviations for the insulation material and its properties, for example heat resistance or suitability for wet conditions.

Source: Lessons in Electric Circuits I: DC (Kuphaldt), 12.3: Conductor Ampacity

Practice wiring and components

Questions last reviewed: 18 October 2026

Red Seal Electrician Practice needs JavaScript to run. Use its questions for practice. The real pass mark is usually 70%. Check it with your province or territory's apprenticeship office.