* Conductor: A material that allows electric current to flow easily through it. This is because conductors have free electrons that can move freely within the material. Examples of solid conductors include metals like copper, silver, and gold.
* Insulator: A material that resists the flow of electric current. Insulators have tightly bound electrons that are not easily freed. Examples of solid insulators include rubber, glass, and plastic.
Important Note: The conductivity of a solid is not an absolute property, but rather a spectrum. Some materials may be better conductors than others, but there's no sharp line dividing "perfect conductors" from "perfect insulators".
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