4. Electrostatics with Conductors

1
4. Electrostatics with Conductors

• General statements about E(x) in or near a
  conductor
• E is 0 inside the conducting material.
• E is normal at the surface.
• The surface charge density is ? ?0En .
• The conductor is an equipotential.
• (Explain why each statement must be true.)

2
4. Electrostatics with Conductors

• The Method of Images
• The image of a charge q in a planar conducting
  surface is a charge q? q located at an equal
  distance on the opposite side of the surface.
• The image of a charge q in a conducting sphere
  of radius a is a charge q? qa/r located at the
  conjugate point, i.e., at radius r? a2/r.
• (Explain why the image charge is not real but a
  useful fiction.)

3
4. Electrostatics with Conductors
In some simple, azimuthally symmetric problems
involving a spherical conducting boundary, the
potential in a charge-free region takes the
form where A, B, C, D are constants that will
be determined by the boundary conditions. Then
the electric field is E ??V .
(Section 4.3)