I did not say that a hemisphere can repel itself. It does not follow from what I wrote. I said "each piece of charge feels the field of a full spherical shell". Of course, not full but minus the infinitesimal piece considered. But the point was that the field is that of a spherical and not...
A hemispherical shell does not have a constant field, not even considering only the field near the outher surface. So, there is no menaingful way of talking about "the field of..." and giving a constant value.
It looks like it may be the result of taking the field of a spherical shell (with...
You don't find the field of one hemisphere but of a sphere. As long as the two pieces "almost touch" the field is of a sphere. For a hemisphere alone there is no simple formula, of course. I don't think the problem in the OP expects to find such a field. Each piece of charge experiences the...
If they are both dashed they are in phase. Half a period later the same point will be reached by two solid lines. The amplitude of the pressure at the point has maximum value. At the constructive interference there is maximum rarefaction too.
You assume that the field is proportional to the current (or voltage). But this will be the case only if the point of interest is always the same relative to the magnet. But here you have the bolt at various distances from the magnet, don't you? Is the suspension point of the bolt fixed as you...
Correct expression for what?
The average velocity is usually defined as ratio of displacement and the time interval the dispalcement happened. ##\vec{V}_{av}=\frac{\Delta\vec{r}}{\Delta t}##. If you want to express the displacement in polar coordinates you have to define what do you mean by...
The voltage you apply cannot accelerate the electrons in the valence band, so it does not transfer energy to them. This why they are not conduction electrons.
Strong electric field may alter the band structure itself though and maybe reduce the band gap.