# Questions tagged [maxwell-equations]

A set of four equations that define electrodynamics. They comprise the Gauss laws for the electric and magnetic fields, the Faraday law, and the Ampère law. Together, these equations uniquely determine the electric and magnetic fields of a physical system. Do not use this tag for the thermodynamical equations known as Maxwell's relations.

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### Confused about Feynman Lectures on attraction between two charges or wire as relativistic phenomenon

I am confused on one of the earlier sections of Feynman Lectures Vol 2. I've posted the relevant snippet below. Since it's in the public domain (http://www.feynmanlectures.caltech.edu/) I think I can ...
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### Volume required to calculate D and H macroscopic variables

For a dielectric, we replace E, B by D, M realizing that the latter pair is a macroscopic property averaged out over a large number of molecules. What is the lower bound on number of molecules or ...
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### What shape does the Induced Electric Field Lines take when in a region there is Non Cylindrical Time Varying Magnetic Field?

Everywhere in the literature I have across, I find that whenever the discussion of the Induced electric field comes, it is discussed around a cylindrical time-varying magnetic field. The induced ...
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### Maxwell and Newton [duplicate]

Has anyone tried to modify Maxwell's electromagnetic field theory so that it is invariant under the Galilean transformation?
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### Rays and the ray equation: behaviour in optical systems, valid solutions to Maxwell's equations

In my studies of geometrical optics, I have encountered variations of the claim that, from what I recall, when the amplitude of the wave is changing slowly, the ray equation is a valid solution to ...
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### Number of independent components of the electromagnetic field

I'm taking a course on electrodynamics and I'm confused when we start talking about potentials. The electromagnetic field seems to have 6 independent components to me. It's described by six dynamical ...
316 views

### Curl of electric field

Related: How is the curl of the electric field possible? According to my information: $$\nabla \times \frac{\hat{r}}{{|\mathbf{r}|}^2} = 0$$ for all $\mathbf{r}$ ( including $\mathbf{r}=0$; ...
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### Sources of Electromagnetic Potentials

I have a question regarding sources of electromagnetic potentials: As far as I know, wave equations for the scalar and magnetic vector potentials can be derived from Maxwell equations employing the ...
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In Ampere's law, the right hand side consists of the surface integral $\int_s\vec j\cdot ds$ which is supposed to represent the current passing through the surface of the enclosed volume. However, $\... 2answers 116 views ### Applying Ampere's law in situation with non-physical$E$-field? On an exam I was given this question: Suppose an electric field in a region with no current$(\textbf{J}=\textbf{0}$) is given by$\textbf{E}(t,x,y,z) = \sin(\omega t)\hat{\textbf{k}}$and$C$is ... 2answers 98 views ### Which Maxwell equation explains how electric engines work While I understand that electric generators (magnetic field$\to$electric current) work according to Maxwell-Faraday law, some people say that electric engines (electric current$\to$magnetic field) ... 2answers 101 views ### Are the boundary conditions purely a consequence of Maxwell's equations? The boundary conditions, namely were all these, realized only by looking at Maxwell's equations? Or is there a physical reasoning behind them? For example, Why does the component of the electric ... 0answers 61 views ### From Maxwell equations to wave equation: what is the meaning of the differentiation? Starting from the Maxwell's equation in empty space and without charges and currents, we can write the two following equations:$\bar \nabla \times \bar E= -{{\partial \bar B}\over{\partial t}}\...
This was a homework problem of mine was: "A coin is placed on its edge in a vertical magnetic field of $B=20$ T. The initial angle between the coin and vertical is $\theta_0=0.1$ rad. Estimate how ...