10. Potentials and Fields Introduction of potential V substantially simplifies finding solutions of problems in Electrostatics. Does such a simplification exist for Electrodynamics as well? Yes, it does: The retarded potentials
Gauge Transformations
Coulomb Gauge Lorentz Gauge Used in electro- and magnetostatics Used in electrodynamics Will be used further on.
Equations for the retarded potentials Inhomogeneous wave equations.
Spherical waves Another, very common solution of the wave equation: Example: sinusoidal spherical wave
Circular wavefronts diverging from a point Source in a ripple tank. Sound waves from a telephone hand set spreading out in air. The waves have been made visible by sweeping out the space in front of the hand set with a light source whose brightness is controlled by a microphone.
Green’s Function Very short and intense pulse:
Retarded Potentials Be careful, the retarded time introduces a new and complicated dependence of
Infinite straight wire
Change of variables in a volume integral
Moving point charge
Lienard-Wiechert potentials
Point charge at constant velocity
The field of a moving point charge field attached to the charge radiated EM wave
Point charge at constant velocity