Dragan Redzic - Academia.edu (original) (raw)
Papers by Dragan Redzic
European Journal of Physics, Sep 25, 2015
For a simple electromagnetic model of a clock introduced by Jefimenko (clock # 1 in 1996 Am. J. P... more For a simple electromagnetic model of a clock introduced by Jefimenko (clock # 1 in 1996 Am. J. Phys. 64 812), a change of the rate of the clock when it is set in uniform motion is calculated exactly, employing the correct equation of motion of a charged particle in the electromagnetic field and the universal boostability assumption. Thus, for the clock under consideration, a dynamical content of the clock retardation is demonstrated. Somewhat surprisingly, the analysis presented discloses that some familiar relativistic generalisations concerning the retardation of clocks have to be amended.
In his first paper on the special theory of relativity, Einstein derived, inter alia, relativisti... more In his first paper on the special theory of relativity, Einstein derived, inter alia, relativistic equations of motion of a charged particle in an external electromagnetic field, employing transformation equations for acceleration and fields components. While correct, the equations he proposed lack conceptual simplicity and generality. A satisfactory, simple and general relativistic equation of motion was first derived by Planck in 1906, who in the next year also presented transformation equations for the Lorentz force expression, in the framework of relativistic electrodynamics. The Planck's equation of motion was promoted by Einstein in his 1907 review paper on special relativity. In the present paper, we give a detailed account of Planck's 1906 succinct derivation which, despite its significance for modern physics, is not expounded in the literature; we reconstruct the missing steps, and outline a direct proof of Lorentz-covariance of the Planck's equation, recalling Tolman's contribution. Both Planck's and Einstein's arguments rest on the assumption that the mass mmm of the charged particle is time-independent Lorentz scalar. We speculate what Einstein, as the protagonist of the theory of relativity, could have inferred about the sought equation of motion if he had employed the weaker assumption that the mass mmm is Lorentz scalar that may depend on the time. We discuss the issue not only without four-tensors, but also from tensorial perspective, employing the generalized relativistic force transformations. While the constancy of mmm remains the fundamental assumption of modern classical electrodynamics, for both pointlike and extended classical charged particle models, the analysis presented might be helpful even if only in clarifying basic concepts.
arXiv (Cornell University), May 17, 2016
The statement that Maxwell's electrodynamics in vacuum is already covariant under Lorentz transfo... more The statement that Maxwell's electrodynamics in vacuum is already covariant under Lorentz transformations is commonplace in the literature. We analyse the actual meaning of that statement and demonstrate that Maxwell's equations are perfectly fit to be Lorentz-covariant; they become Lorentz-covariant if we construct to be so, by postulating certain transformation properties of field functions. In Aristotelian terms, the covariance is a plain potentiality, but not necessarily entelechy.
European Journal of Physics, Aug 15, 2018
European Journal of Physics, 2016
In a general gauge choice fixing the divergence of the vector potential, an explicit retarded sol... more In a general gauge choice fixing the divergence of the vector potential, an explicit retarded solution of the corresponding dynamical equations for the electromagnetic potentials satisfies the gauge choice if and only if the continuity equation is satisfied.
European Journal of Physics, 2017
European Journal of Physics, 2016
The statement that Maxwell's electrodynamics in vacuum is already covariant under Lorentz transfo... more The statement that Maxwell's electrodynamics in vacuum is already covariant under Lorentz transformations is commonplace in the literature. We analyse the actual meaning of that statement and demonstrate that Maxwell's equations are perfectly fit to be Lorentz-covariant; they become Lorentz-covariant if we construct to be so, by postulating certain transformation properties of field functions. In Aristotelian terms, the covariance is a plain potentiality, but not necessarily entelechy.
American Journal of Physics, Mar 1, 1992
American Journal of Physics, Dec 1, 1993
European Journal of Physics, Nov 26, 2009
Some errors are rectified in a recent paper by van Kampen (2008 Eur. J. Phys. 29 879-83) on the f... more Some errors are rectified in a recent paper by van Kampen (2008 Eur. J. Phys. 29 879-83) on the force between two parallel current-carrying wires.
American Journal of Physics, Feb 1, 1994
European Journal of Physics, Mar 25, 2008
ABSTRACT The thread-between-spaceships problem is analysed both in its 'mild' var... more ABSTRACT The thread-between-spaceships problem is analysed both in its 'mild' variant (after some time the ships' acceleration ceases and they coast at the same constant speed, with respect to the lab frame), and in a special case of its 'tough' variant (the ships' acceleration never ceases). It is pointed out that in the special case of the tough variant the thread connecting spaceships may never break, regardless of how close the ships' speed approaches c.
American Journal of Physics, Jun 1, 1992
It is shown that a conducting spheroid, which is moving uniformly along its axis of revolution, p... more It is shown that a conducting spheroid, which is moving uniformly along its axis of revolution, produces the same electromagnetic field as a moving line charge or a point charge or a charged disk, depending on the shape of the spheroid.
European Journal of Physics, Jan 8, 2008
An attempt is made to elucidate the essence of relativistic length contraction by scrutinizing it... more An attempt is made to elucidate the essence of relativistic length contraction by scrutinizing its various interpretations that appear in the literature.
![Research paper thumbnail of Comment on ‘‘Electrostatic images by multipole expansion’’ by J. L. Marin and R. Rosas [Am. J. Phys. 52, 358–361 (1984)]](https://attachments.academia-assets.com/104407849/thumbnails/1.jpg)
](American Journal of Physics, 1994
European Journal of Physics
Aguirregabiria et al (2022 Eur. J. Phys. 43 035603) obtain the Lorentz transformations and the tr... more Aguirregabiria et al (2022 Eur. J. Phys. 43 035603) obtain the Lorentz transformations and the transformation equations for the electric and magnetic fields, and charge and current density, by restricting the principle of relativity to Maxwell’s equations in vacuum. We rectify and simplify their argument.
A novel definition of the Laplacian of 1/r is presented, suitable for advanced undergraduates.
European Journal of Physics, Sep 25, 2015
For a simple electromagnetic model of a clock introduced by Jefimenko (clock # 1 in 1996 Am. J. P... more For a simple electromagnetic model of a clock introduced by Jefimenko (clock # 1 in 1996 Am. J. Phys. 64 812), a change of the rate of the clock when it is set in uniform motion is calculated exactly, employing the correct equation of motion of a charged particle in the electromagnetic field and the universal boostability assumption. Thus, for the clock under consideration, a dynamical content of the clock retardation is demonstrated. Somewhat surprisingly, the analysis presented discloses that some familiar relativistic generalisations concerning the retardation of clocks have to be amended.
In his first paper on the special theory of relativity, Einstein derived, inter alia, relativisti... more In his first paper on the special theory of relativity, Einstein derived, inter alia, relativistic equations of motion of a charged particle in an external electromagnetic field, employing transformation equations for acceleration and fields components. While correct, the equations he proposed lack conceptual simplicity and generality. A satisfactory, simple and general relativistic equation of motion was first derived by Planck in 1906, who in the next year also presented transformation equations for the Lorentz force expression, in the framework of relativistic electrodynamics. The Planck's equation of motion was promoted by Einstein in his 1907 review paper on special relativity. In the present paper, we give a detailed account of Planck's 1906 succinct derivation which, despite its significance for modern physics, is not expounded in the literature; we reconstruct the missing steps, and outline a direct proof of Lorentz-covariance of the Planck's equation, recalling Tolman's contribution. Both Planck's and Einstein's arguments rest on the assumption that the mass mmm of the charged particle is time-independent Lorentz scalar. We speculate what Einstein, as the protagonist of the theory of relativity, could have inferred about the sought equation of motion if he had employed the weaker assumption that the mass mmm is Lorentz scalar that may depend on the time. We discuss the issue not only without four-tensors, but also from tensorial perspective, employing the generalized relativistic force transformations. While the constancy of mmm remains the fundamental assumption of modern classical electrodynamics, for both pointlike and extended classical charged particle models, the analysis presented might be helpful even if only in clarifying basic concepts.
arXiv (Cornell University), May 17, 2016
The statement that Maxwell's electrodynamics in vacuum is already covariant under Lorentz transfo... more The statement that Maxwell's electrodynamics in vacuum is already covariant under Lorentz transformations is commonplace in the literature. We analyse the actual meaning of that statement and demonstrate that Maxwell's equations are perfectly fit to be Lorentz-covariant; they become Lorentz-covariant if we construct to be so, by postulating certain transformation properties of field functions. In Aristotelian terms, the covariance is a plain potentiality, but not necessarily entelechy.
European Journal of Physics, Aug 15, 2018
European Journal of Physics, 2016
In a general gauge choice fixing the divergence of the vector potential, an explicit retarded sol... more In a general gauge choice fixing the divergence of the vector potential, an explicit retarded solution of the corresponding dynamical equations for the electromagnetic potentials satisfies the gauge choice if and only if the continuity equation is satisfied.
European Journal of Physics, 2017
European Journal of Physics, 2016
The statement that Maxwell's electrodynamics in vacuum is already covariant under Lorentz transfo... more The statement that Maxwell's electrodynamics in vacuum is already covariant under Lorentz transformations is commonplace in the literature. We analyse the actual meaning of that statement and demonstrate that Maxwell's equations are perfectly fit to be Lorentz-covariant; they become Lorentz-covariant if we construct to be so, by postulating certain transformation properties of field functions. In Aristotelian terms, the covariance is a plain potentiality, but not necessarily entelechy.
American Journal of Physics, Mar 1, 1992
American Journal of Physics, Dec 1, 1993
European Journal of Physics, Nov 26, 2009
Some errors are rectified in a recent paper by van Kampen (2008 Eur. J. Phys. 29 879-83) on the f... more Some errors are rectified in a recent paper by van Kampen (2008 Eur. J. Phys. 29 879-83) on the force between two parallel current-carrying wires.
American Journal of Physics, Feb 1, 1994
European Journal of Physics, Mar 25, 2008
ABSTRACT The thread-between-spaceships problem is analysed both in its 'mild' var... more ABSTRACT The thread-between-spaceships problem is analysed both in its 'mild' variant (after some time the ships' acceleration ceases and they coast at the same constant speed, with respect to the lab frame), and in a special case of its 'tough' variant (the ships' acceleration never ceases). It is pointed out that in the special case of the tough variant the thread connecting spaceships may never break, regardless of how close the ships' speed approaches c.
American Journal of Physics, Jun 1, 1992
It is shown that a conducting spheroid, which is moving uniformly along its axis of revolution, p... more It is shown that a conducting spheroid, which is moving uniformly along its axis of revolution, produces the same electromagnetic field as a moving line charge or a point charge or a charged disk, depending on the shape of the spheroid.
European Journal of Physics, Jan 8, 2008
An attempt is made to elucidate the essence of relativistic length contraction by scrutinizing it... more An attempt is made to elucidate the essence of relativistic length contraction by scrutinizing its various interpretations that appear in the literature.
American Journal of Physics, 1994
European Journal of Physics
Aguirregabiria et al (2022 Eur. J. Phys. 43 035603) obtain the Lorentz transformations and the tr... more Aguirregabiria et al (2022 Eur. J. Phys. 43 035603) obtain the Lorentz transformations and the transformation equations for the electric and magnetic fields, and charge and current density, by restricting the principle of relativity to Maxwell’s equations in vacuum. We rectify and simplify their argument.
A novel definition of the Laplacian of 1/r is presented, suitable for advanced undergraduates.