Push-in terminal connection means in snap switches are primarily permitted for which type of conductors?

The push-in terminal connection in snap switches is primarily designed for solid copper conductors. This preference stems from the physical properties and conductivity characteristics of solid copper, which allows for reliable and effective connections without the need for additional mechanical means of securing the wire. Solid copper has better conductivity compared to aluminum and is less prone to breakage or loosening over time, which is critical for maintaining a safe and functional electrical connection.

Aluminum conductors, while used in certain applications, do not lend themselves as well to push-in connections due to their different expansion properties and susceptibility to oxidation, which can lead to poor connections and potential safety hazards. Copper-clad aluminum is another type that combines these issues, and the performance may not be consistent with solid copper in push-in applications.

Thus, focusing on solid copper ensures that the connection remains secure and effective over time in snap switches, making it the correct answer.