* Conductors: Conductors are excellent at building up a charge *on their surface*. This is because electrons can move freely within the material, allowing them to redistribute and accumulate on the surface when exposed to an external electric field. Think of rubbing a balloon on your hair: the electrons move from your hair to the balloon, creating a static charge.
* Insulators: Insulators, on the other hand, are terrible conductors. Electrons are tightly bound within the material, making it difficult for them to move. However, insulators can still build up a charge *internally*. When an insulator is exposed to an electric field, the electrons within the material shift slightly, creating a separation of charge within the material itself. This is called "polarization" and it is responsible for the attraction between an insulator and a charged object (like a charged balloon sticking to a wall).
In summary:
* Conductors: Build up charge *on their surface* due to the free movement of electrons.
* Insulators: Build up charge *internally* due to polarization.
Both conductors and insulators can build up a charge, but the mechanism and the location of the charge are different.
