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Field of a conductor
Intermediate
Inside a conductor E is zero; at the surface E = σ/ε₀.
In electrostatic equilibrium the field inside a conductor is zero, charge resides on the surface, and the field just outside is perpendicular to the surface with E = σ/ε₀.
Charges concentrate at sharp points (lightning rods).
These conditions assume no current flowing.
In more detail
In electrostatic equilibrium, the field inside a conductor is zero, and any excess charge resides on its surface. The field just outside the surface is perpendicular to the surface.
Real-world uses
- Lightning rods and metal cages protect against electric fields.
- Shielding sensitive electronics uses conductors.
- Engineers designing lightning rods and high-voltage terminals rely on the fact that charges gather at the surface of conductors.
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Frequently asked questions
Why is the field zero inside a conductor?
Because free charges move until they cancel any internal field.
Why is charge concentrated at points?
The surface charge density is largest where the curvature is greatest.
Why is the field zero inside a conductor?
Free charges move until they cancel the field inside, so in equilibrium no field remains there.
Related topics in Electrostatics
Field of infinite plane sheet · Field of a charged shell · Field of a uniformly charged sphere · Electrostatic shielding · Electric potential · Potential difference