What characteristic makes copper an effective material in electrical applications?

Copper's effectiveness in electrical applications primarily stems from its status as a good conductor of electricity. This means that it allows electric current to flow through it with minimal resistance, which is essential for efficient power transmission and distribution. High electrical conductivity ensures that energy losses as heat are kept to a minimum, making copper an ideal choice for wiring, electrical components, and circuit boards.

The other options do not align with the fundamental properties that make copper suitable for electrical applications. While some materials may be lightweight or non-reactive, these characteristics do not directly relate to how well a material conducts electricity. Additionally, insulators serve a different purpose by preventing the flow of electrical current, which is contrary to the desired property of conductors like copper.