Snap switches with 'push-in' terminal connections are generally only permitted for use with which conductors?

• A. Solid copper
• B. Solid aluminum
• C. Copper-clad aluminum
• D. Copper coated steel

Answer: (A)

Push-in terminals rely on a spring clamp to bite into a solid conductor, creating a clean, stable contact that stays tight through temperature changes and vibrations. Solid copper has the right combination of ductility, conductivity, and predictable oxidation behavior to maintain a low-resistance connection in these terminals over time. Aluminum oxidizes more readily and can creep and loosen under heat cycling, which compromises the connection. Copper-clad aluminum and copper-coated steel introduce mixed metals that can corrode or lose the solid, uniform contact the clamp needs, making them unreliable in push-in designs. That’s why solid copper is the approved conductor for these snap switches.