Electrons move easily in good conductors and poorly in good insulators.
Outer electrons of the atoms in a metal are not anchored to the nuclei of particular atoms, but are free to roam in the material.
Materials through which electric charge can flow are called conductors.
Metals are good conductors for the motion of electric charges because their electrons are “loose.”
Electrons in other materials—rubber and glass, for example—are tightly bound and remain with particular atoms.
They are not free to wander about to other atoms in the material.
These materials, known as insulators, are poor conductors of electricity.
A substance is classified as a conductor or an insulator based on how tightly the atoms of the substance hold their electrons.
The conductivity of a metal can be more than a million trillion times greater than the conductivity of an insulator such as glass.
In power lines, charge flows much more easily through hundreds of kilometers of metal wire than through the few centimeters of insulating material that separates the wire from the supporting tower.
Materials that don't hold electrons tightly lose them to materials that hold electrons more tightly.
Semiconductors are materials that can be made to behave sometimes as insulators and sometimes as conductors.
Atoms in a semiconductor hold their electrons until given small energy boosts.
This occurs in photovoltaic cells that convert solar energy into electrical energy.
Thin layers of semiconducting materials sandwiched together make up transistors.
