What type of copper conductor is known for having the lowest conductivity and highest resistivity?

Hard-drawn copper conductors are known for having the lowest conductivity and the highest resistivity among the types listed. This is primarily due to the manufacturing process they undergo. Hard-drawn conductors are pulled through a die, which increases their strength and hardness, but this also aligns the copper atoms in a way that increases resistance to the flow of electric current.

As a result, the atomic structure becomes less conducive to carrying electrical charges compared to softer forms of copper, such as soft-drawn or annealed copper, which have greater conductivity due to their more favorable atomic arrangement. Soft-drawn and annealed copper undergo processes that relieve stresses and enhance the material's ductility, allowing for greater electron mobility.

Extruded copper can also vary in its properties depending on the specifics of the extrusion process, but hard-drawn copper's characteristics are distinctly noted for their lower conductivity due to the increased resistivity from the mechanical treatment it receives. Therefore, hard-drawn copper stands out in this context for its specific electrical properties.