The Electromagnetic Field
The
evolution of a mathematical description of the electric and magnetic forces and
induction phenomena associated with electric charge and current is a
fascinating chapter in the history of electromagnetic field theory. It was not
until the early nineteenth century that long known, but unrelated, electric and
magnetic phenomena were interconnected. Michael Faraday, by an unusual series
of insightful experiments, conceived a pictorial description of electric and magnetic
phenomena in terms of lines of force. This picture so influenced James Clerk Maxwell
that he devoted many months to translating Faraday’s vision into a set of
mathematical equations, which for the first time defined the remarkably
accurate space-time dependent electromagnetic field. Although it is frequently
customary to regard the Maxwell Equations as “God given”, the following review
attempts their derivation via physically intuitive experimental procedures.
Charges and
currents (moving charges) are sources that excite space-time dependent force
and induction phenomena at each point in the space surrounding these charges. Electric
and magnetic observables, which describe the magnitude and direction of force
and induction phenomena in a region of space-time, form the essence of the
electromagnetic field. Faraday’s vision
of the field excited by electric and magnetic charges was in terms of lines of
force that arise and end on these charges.
Tensions along and pressures transverse to these lines, together with
their motion, provided Faraday with a visual basis for describing various
dynamical phenomena taking place in an electromagnetic field --but not
completely. It remained for Maxwell, to symbolize mathematically the lines of
force picture, and to complete the Faraday picture by adding the concept of an
electric displacement current. This addition led to the identification of
electromagnetic wave phenomena as light!
The
following provides a brief review of static and dynamic features of the
Electromagnetic field:
Fields of electric and magnetic charges(static electric and magnetic fields).
Fields of electric and magnetic
currents (concept of duality of currents).
Time-varying fields (radiation
and force phenomena)
Electromagnetic
Applications:
Electromagnetic pulse transmission
and Reflection