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Results tagged with electromagnetism
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user 271720
The classical theory of electric and magnetic fields, both in the static and dynamic case. It also covers general questions about magnets, electric attraction/repulsion, etc. Distinct from electrical-engineering.
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Why do charges accumulate at the surface and at the the tip of the needle?
If we place a positive charge on a conductor, why will the charges distribute themselves only on the surface and why is the distribution uneven like for the second image describing a needle? (This is …
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Why isn't the magnetic field density zero here?
In my lecture notes for magnetostatics, my professor has this explanation of why H is not necessarily $0$ that I dont understand.
$$\nabla \times \bf{H} = \bf{J} \\ \bf{J}=0 \Rightarrow \nabla \times …
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Eelectric and magnetic field inside a conductor cavity
Assume we have an external field outside a conductor that has cavity inside. I know that E field is 0 inside that cavity for electrostatic and time varying case but I dont understand what happens to t …
- 285
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Faraday's law. Why does the induced current flow this way?
We have this stationary loop in a time-varying B-field. The current I (in red) is induced by the changing field B(t). This current in turn induces a B field that opposes the changing field due to righ …
- 285
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340
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Electric field inside uniformly distributed charges
One of the problems I was solving states that "By Gauss’ law the electric field inside a sphere of uniformly distributed charges is 0". I don't understand how that is possible. I thought that this was …
- 285
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Equation of Continuity statements I dont understand
There are two statements about Equation of Continuity in my professors notes that I don't understand.
$$ \nabla \cdot \textbf{J} = - \frac{\partial\rho}{\partial t} $$
The Equation of Continuity can …
- 285
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How is magnetic dipole "created"?
I know that the electric dipole can be created when the electron cloud is displaced realative to the nucleus. I am trying to draw parallel to this and to better understand this topic, so please help m …
- 285
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Trouble with enterpreting Faraday's Law
$$ \nabla \times \textbf{E} = -\frac{\partial \textbf{B}}{\partial t} $$
My interpretation of this equation is that:
A steady magnetic field will result in an electric field that is $0$.
A varying ma …
- 285
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Charge density in a conducting sphere
We charge a conductive sphere with charge $Q$. Charges on a charged conductive sphere go towards the surface so then the volume charge density is 0 which makes surface charge density $Q$. Is my statem …
- 285
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3
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Why is the curl of magnetic field $0$ outside the conductor and non-zero inside? [duplicate]
I dont understand why the magnetic field does not curl outside the cable, according to this example, since I would expect the magnetic field lines to go back on themselves around the cable like shown …
- 285
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Where does one more '$\rm m$' come from in the units?
$$\nabla \times A = B$$
$A$ is vector magnetic potential, $\mathrm{Wb/m}$
$B$ is magnetic field intensity, $\mathrm{Wb/m^2}$
Where does one more m come from for $B$? Is that from the gradient operator …
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Polarization of a material
Can someone explain where this minus comes from? Aren't $a_R$ and $a_n$ parallel so the dot product should be 1. The radius increases outwards aswell as the surface $a_n$, right?
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