A copper connecting wire and a thin pencil lead (graphite) are both used in electrical circuits. Describe and explain the difference in resistance between the copper wire and the pencil lead, referring to the structure of each material and how charge carriers move through them.

Copper has a lower resistance than graphite.

Copper is a metal with a crystalline lattice in which the outer‑shell electrons are delocalised and form a "sea" of free electrons that can move easily through the lattice.

Graphite is a non‑metal with a layered structure; each carbon atom is bonded to three others in a plane, leaving one “p” electron per atom that can move only within the layers.

Because copper has many more free electrons than graphite, the number of charge carriers in copper is far greater.

Fewer charge carriers in graphite mean that, for a given electric field, the current density is lower and the current is harder to drive through the material.

Additionally, electrons in graphite collide more frequently with the lattice ions and with the interlayer boundaries, giving a higher resistivity.

Thus copper’s high density of free electrons and fewer collisions give it a much lower resistance than the pencil lead.