A material through which electric current does not pass easily is called an insulator.

Here are some examples of insulators:

* Rubber: Used in electrical cords and gloves.

* Glass: Used in light bulbs and other electrical components.

* Plastic: Used in many electrical devices and coverings.

* Wood: A common insulator used in construction.

* Air: Acts as an insulator under normal conditions.

* Diamond: An excellent insulator due to its tightly bound electrons.

Insulators have a high resistance to the flow of electricity because their electrons are tightly bound to their atoms and cannot move freely. This makes it difficult for an electric current to pass through them.