1-4 Missouri Valley Practice Test 2026 - Free Practice Questions and Study Guide

The key idea is that these cross arms act as insulators. Wood and fiberglass resist the flow of electric current, meaning they have high electrical resistance and do not readily conduct electricity. That insulating property keeps the live conductors from energizing the pole itself or leaking current into the surroundings, which is essential for safety and reliability in a power system. Decay resistance and superior mechanical strength matter for durability, but they don’t explain why electricity stays away from the arm. High conductivity would be the opposite of what we want here—an electrical path through the arm would be dangerous.