Conductors vs insulators (spec 2.22P)
Free electrons or not.
Conductors β materials that contain free-moving charge carriers (usually electrons). Current flows easily.
- Metals: copper (used for wires), silver (best but expensive), aluminium (overhead power cables), gold (corrosion-resistant contacts in electronics).
- Carbon (graphite) β surprising conductor for a non-metal.
Insulators β materials with no free electrons. Current does NOT flow easily.
- Plastics: PVC, polythene, polystyrene.
- Other: glass, ceramic, dry wood, rubber, pure water (tap water is a poor conductor due to dissolved ions).
Why this matters for electrostatics. Insulators CAN be charged by friction because the transferred electrons can't escape (no free path). Conductors held in the hand CANNOT β any electrons transferred immediately leak through your body to the ground.
To charge a metal rod, hold it via an INSULATING HANDLE so the charge can't drain to earth.
- Conductors = free electrons (metals, graphite).
- Insulators = no free electrons (plastic, glass).
- Insulators easy to charge; conductors leak charge.