2,228 research outputs found
Electromagnetics from a quasistatic perspective
Quasistatics is introduced so that it fits smoothly into the standard
textbook presentation of electrodynamics. The usual path from statics to
general electrodynamics is rather short and surprisingly simple. A closer look
reveals however that it is not without confusing issues as has been illustrated
by many contributions to this Journal. Quasistatic theory is conceptually
useful by providing an intermediate level in between statics and the full set
of Maxwell's equations. Quasistatics is easier than general electrodynamics and
in some ways more similar to statics. It is however, in terms of interesting
physics and important applications, far richer than statics. Quasistatics is
much used in electromagnetic modeling, an activity that today is possible on a
PC and which also has great pedagogical potential. The use of electromagnetic
simulations in teaching gives additional support for the importance of
quasistatics. This activity may also motivate some change of focus in the
presentation of basic electrodynamics
On Essential Incompleteness of Hertz's Experiments on Propagation of Electromagnetic Interactions
The historical background of the 19th century electromagnetic theory is
revisited from the standpoint of the opposition between alternative approaches
in respect to the problem of interactions. The 19th century electrodynamics
became the battle-field of a paramount importance to test existing conceptions
of interactions. Hertz's experiments were designed to bring a solid
experimental evidence in favor of one of them. The modern scientific method
applied to analyze Hertz's experimental approach as well as the analysis of his
laboratory notes, dairy and private letters show that Hertz's
"\textit{crucial}" experiments cannot be considered as conclusive at many
points as it is generally implied. We found that alternative Helmholtz's
electrodynamics did not contradict any of Hertz's experimental observations of
transverse components as Maxwell's theory predicted. Moreover, as we now know
from recently published Hertz's dairy and private notes, his first experimental
results indicated clearly on infinite rate of propagation. Nevertheless,
Hertz's experiments provided no further explicit information on non-local
longitudinal components which were such an essential feature of Helmholtz's
theory. Necessary and sufficient conditions for a decisive choice on the
adequate account of electromagnetic interactions are discussed from the
position of modern scientific method
Convection displacement current and alternative form of Maxwell-Lorentz equations
Some mathematical inconsistencies in the conventional form of Maxwell's
equations extended by Lorentz for a single charge system are discussed. To
surmount these in framework of Maxwellian theory, a novel convection
displacement current is considered as additional and complementary to the
famous Maxwell displacement current. It is shown that this form of the
Maxwell-Lorentz equations is similar to that proposed by Hertz for
electrodynamics of bodies in motion. Original Maxwell's equations can be
considered as a valid approximation for a continuous and closed (or going to
infinity) conduction current. It is also proved that our novel form of the
Maxwell-Lorentz equations is relativistically invariant. In particular, a
relativistically invariant gauge for quasistatic fields has been found to
replace the non-invariant Coulomb gauge. The new gauge condition contains the
famous relationship between electric and magnetic potentials for one uniformly
moving charge that is usually attributed to the Lorentz transformations. Thus,
for the first time, using the convection displacement current, a physical
interpretation is given to the relationship between the components of the
four-vector of quasistatic potentials. A rigorous application of the new gauge
transformation with the Lorentz gauge transforms the basic field equations into
an independent pair of differential equations responsible for longitudinal and
transverse fields, respectively. The longitudinal components can be interpreted
exclusively from the standpoint of the instantaneous "action at a distance"
concept and leads to necessary conceptual revision of the conventional
Faraday-Maxwell field. The concept of electrodynamic dualism is proposed for
self-consistent classical electrodynamics. It implies simultaneous coexistenceComment: ReVTeX file, 29pp., no figure
Electrodynamics of a Cosmic Dark Fluid
Cosmic Dark Fluid is considered as a non-stationary medium, in which
electromagnetic waves propagate, and magneto-electric field structures emerge
and evolve. A medium - type representation of the Dark Fluid allows us to
involve into analysis the concepts and mathematical formalism elaborated in the
framework of classical covariant electrodynamics of continua, and to
distinguish dark analogs of well-known medium-effects, such as optical
activity, pyro-electricity, piezo-magnetism, electro- and magneto-striction and
dynamo-optical activity. The Dark Fluid is assumed to be formed by a duet of a
Dark Matter (a pseudoscalar axionic constituent) and Dark Energy (a scalar
element); respectively, we distinguish electrodynamic effects induced by these
two constituents of the Dark Fluid. The review contains discussions of ten
models, which describe electrodynamic effects induced by Dark Matter and/or
Dark Energy. The models are accompanied by examples of exact solutions to the
master equations, correspondingly extended; applications are considered for
cosmology and space-times with spherical and pp-wave symmetries. In these
applications we focused the attention on three main electromagnetic phenomena
induced by the Dark Fluid: first, emergence of Longitudinal Magneto-Electric
Clusters; second, generation of anomalous electromagnetic responses; third,
formation of Dark Epochs in the Universe history.Comment: 39 pages, 0 figures, replaced by the version published in MDPI
Journal "Symmetry" (Special Issue: Symmetry: Feature Papers 2016); typos
correcte
Vito Volterra and his commemoration for the centenary of Faraday's discovery of electromagnetic induction
The paper presents a memoir of 1931 written by Vito Volterra on the Italian
physicists of the nineteenth century and the researches these scientists made
after the discoveries of Michael Faraday on electromagnetism. Here, the memoir
entitled "I fisici italiani e le ricerche di Faraday" is translated from
Italian. It was written to commemorate the centenary of Faraday's discovery of
the electromagnetic induction. Besides being a remarkable article on the
history of science, it was also, in a certain extent, a political paper. In
fact, in 1931, the same year of the publication of this article, Mussolini
imposed a mandatory oath of loyalty to Italian academies. Volterra was one of
the very few professors who refused to take this oath of loyalty. Because of
the political situation in Italy, Volterra wanted to end his paper sending a
message to the scientists of the world, telling that the feeling of admiration
and gratitude that in Italy the scientists had towards "the great thinker and
British experimentalist" was profound and unanimous.Comment: Volterra's original paper at
http://www.liberliber.it/online/autori/autori-v/vito-volterra/i-fisici-italiani-e-le-ricerche-di-Faraday
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