Conductors vs Insulators — How Materials Handle Electric Charge
Conductors
Materials with free charge carriers (usually electrons) that move easily under an electric field. Metals are the classic conductors — copper's resistivity is about 1.7×10⁻⁸ Ω·m.
Unit: ohm-meter (Ω·m)
Example: Copper wires carry current from the power plant to your home with little loss because copper's free electrons drift readily.
Insulators
Materials whose electrons are tightly bound to atoms, so almost no charge flows. Rubber, glass and dry air are insulators, with resistivities around 10¹⁰–10¹⁶ Ω·m.
Unit: ohm-meter (Ω·m)
Example: The rubber coating on a power cord keeps the current inside the copper wire — and your hands safe — because its electrons can't move freely.
Key differences
| Aspect | Conductors | Insulators |
|---|---|---|
| Charge carriers | Abundant free electrons | Essentially none — electrons bound to atoms |
| Resistivity | Very low (~10⁻⁸ Ω·m) | Enormous (~10¹⁰–10¹⁶ Ω·m) |
| Atomic picture | Overlapping energy bands let electrons roam | Large band gap locks electrons in place |
| Temperature effect | Resistivity rises as atoms vibrate more | Resistivity usually falls slightly (a few carriers get freed) |
| In between | — | Semiconductors sit between the two and can be tuned — the basis of all electronics |
| Typical uses | Wires, contacts, electrodes | Coatings, spacers, circuit boards, safety gear |
Insulators are not perfect — enough voltage forces current through any material (that's what lightning does to air). 'Insulator' means enormous resistance under normal conditions, not infinite resistance always.