# Questions tagged [classical-electrodynamics]

Classical electrodynamics is the discipline that studies electromagnetic phenomena – such as electric and magnetic fields, radiation, and the dynamics of charged bodies – in classical terms.

914 questions
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### Lagrangian of Charged Particle Evaluated On-Shell

I am trying to calculate the Lagrangian of a charged particle in background gauge field evaluaed on-shell. Let $A^{\mu}(x)$ be a gauge field. The action of a charged particle in this background gauge ...
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### Conservation law charge in plane-wave

When considering a charged particle in a plane-wave field, it is possible to show that the 2 following quantities are conserved $\boldsymbol{p}_{\perp} - e\boldsymbol{A}_{\perp}$ and $p_z - \gamma$ ...
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### Motion of a particle near a charged plane

Consider a positive charge density in the $x-y$ plane, its electric field is $\vec{E}=\frac{\sigma}{2\epsilon_0}\hat{z}$. At moment $t=0$ a particle with positive charge $q$ begins to move with ...
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### Magnetic field from displacement currents in a capacitor, and an applied exterior magnetic field

If an exterior magnetic field ($B$) is applied to oppose or support the magnetic field produced by the displacement currents ($B_D$), what would happen to the electric field within the gap? And the ...
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### Moving a conductor with the presence of both E & B fields?

If a conductor is charged from an exterior electric field, moved in a magnetic field perpendicular to the E-Field, the velocity's direction is also perpendicular to both the B-field and E-field. How ...
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### Magnetic field induced from the conductive capacitor plates?

If a capacitor is being charged or in the process of discharge, there is current flowing in/out of the conductive plate, besides the magnetic field produced by the displacement currents($B_{dc}$) in ...
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### Why do thermal hotspots in a metallic nanoparticle do not match it's optical hotspots?

I am a little bit confused here. When a metallic nanoparticle is impinged with light at its resonance, the electric field is greatly enhanced at the surface along the polarisation of the wave(suppose ...
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### Why is beam forming more energy efficient than a straight up omnidirectional signal?

Someone tried to explain the process of beam forming to me, and how beam forming is far more efficient than an omnidirectional signal of similar amplitude. This seemed obvious at the time: the power ...