Conductors

Summary

• When the charges on an electrical conductor are in static equilibrium…
  • the net charge resides on the outer surface.
    • Charges move as far to the outside as they can go.
  • the electric field outside is perpendicular to the surface.
    • A parallel component of the field would mean the charges are still being pushed into their equilibrium position.
  • the electric field inside is zero or, equivalently, the electric potential (voltage) inside is uniform.
    • This phenomenon is the basis of electromagnetic shielding, also known as a Faraday cage.
• Pointed conductors (including sharp edges or corners)
  • Static charge concentrates near the pointed parts of a conductor.
    • This phenomenon is the basis of corona discharge — the increased rate of charge dissipation near the pointed regions of a conductor.
• Parallel conducting plates
  • The field between two oppositely charged, parallel conducting plates is uniform.
• Charge on conductors in contact will move until the electric potential (voltage) on each is everywhere the same.
  • Charge arranges itself so that more charge is found on the larger conductor.
    • This phenomenon is the basis of grounding (US) or earthing (UK) — the transfer of charge from a charged object to a significantly larger neutral object (like the Earth).