Electrostatics with conductors
Funny, didn’t realize this was a separate topic later; we saw some of these in reviewing for the electric fields test and it made people worried... now we get to go over this again.
You should be able to describe the charge distribution within a conductor in an electrostatic situation.
Charge distribution within a conductor
An ideal conductor is a material in which electrons (or other charge carriers) are able to move freely. In real conductors, there is some resistance to the movement of electrons which we will discuss later. Materials like metal are good conductors; the atoms are in a lattice structure, each with an outer shell of electrons that can freely dissociate from their parent atom and travel through the lattice
When a conductor is in electrostatic equilibrium, mutual repulsion of excess charge carriers results in those charge carriers residing entirely on the surface of the conductor.
In electrostatic equilibrium, excess charge resides on the surface of a conductor
In a conductor with a negative net charge, excess electrons reside on the surface of the conductor. In a conductor with a positive net charge, the surface becomes deficient or depleted in electrons, and can be modeled as if positive charge carriers reside on the surface of the conductor. Excess charges will move to the surface of a conductor to create a state of electrostatic equilibrium within the conductor.
The time interval over which charges reach electrostatic equilibrium within a conductor is so short as to be negligible.
When a conductor reaches electrostatic equilibrium, all points on the surface of the conductor have the same electric potential, and the conductor becomes an equipotential surface.
The charge density on the surface of a conductor will be greater where there are points or edges compared to planar areas.
Electric field for a conductor in electrostatic equilibrium
All excess charges reside on the surface of a conductor, which means there is no net charge in the interior of the conductor, and the electric field is zero within the conductor.
Since the surface is an equipotential surface, the electric field is perpendicular to the outer surface of a conductor.
A conductor can be polarized in the presence of an external electric field. This is a consequence of the conductor remaining an equipotential surface.
Electrostatic shielding and Faraday Cages
Electrostatic shielding is the process of surrounding an area with a closed, conducting shell to create a region inside the conductor that is free from external electric fields.
See also
- list here