Which pairing of behavior and class is correct?
Copper and glass are both packed with electrons. Every atom of each has them. Yet charge streams through copper and goes nowhere in glass.
The difference is not whether electrons are there. It is whether any of them can move. This lesson explains the pattern you have just sorted: what a metal has that an insulator lacks.
Start inside the metal. In copper, some electrons are not held to any one atom.
Those electrons can drift from atom to atom, through the whole piece of metal.
Electrons that are free to move through a material like this are called free electrons.
Each electron carries electric charge. So when copper's free electrons drift along a wire, charge flows along the wire. That flow is a current.
Apply a voltage across the wire, and the free electrons drift along it. That is why copper conducts. The free electrons are the moving charges that carry the current: the metal's mobile charge carriers.
Which particles carry the current through a steel wire?
Now the glass. In glass, every electron is held tightly to its own atom.
Nothing in the glass is free to move, so almost no charge can flow. That is why glass insulates.
An extension cord's core is aluminum. Explain why the aluminum conducts electricity.
Name what aluminum has:
Aluminum is a metal, so some of its electrons are free to move through it.
Say what they do:
Each electron carries charge. When a voltage is applied, the free electrons drift along the cord.
Moving charge is a current.
Aluminum conducts because its free electrons drift along the cord and carry the charge.
Brass conducts electricity. Why?
A ceramic mug is full of electrons, yet it carries almost no current. Explain why.
Name what ceramic lacks:
In ceramic, every electron is held tightly to its own atom.
Say what follows:
No charge in the ceramic is free to move, so almost no charge can flow.
The mug barely conducts because almost none of its electrons are free to move.
Glass barely conducts, yet glass is full of electrons. What stops charge flowing through glass?
A silver spoon conducts electricity. Which statement explains why?
A copper wire carries a current. Which statement describes what is moving?
A rubber band has electrons in every atom, but it cannot carry a current. What does rubber lack?