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There is a sort of analog called gravitomagnetism (or gravitoelectromagnetism), but it is not discussed that often because it applies only in a special case. It is an approximation of general relativity (i.e. the Einstein Field Equations) in the case where: The weak field limit applies. The correct reference frame is chosen (it's not entirely clear to me ...

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There is a gravitational analogue of the magnetic field. See gravitoelectromagnetism and frame dragging on Wikipedia.

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Electric field is a vector quantity. So, treat them as vectors and find the vector sum of the electric fields. $$\vec{E}_{net}=\vec{E}_{1}+\vec{E}_{2}+\vec{E}_{3}$$

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I think I can clear up most of this. Maybe someone whose qm chops are better than mine could help with the parts I'm fuzzy on. Suppose an even-even nucleus has a prolate deformation (like an American football). This is very common, and basically occurs for any nucleus whose N and Z are both far from any magic numbers. What we really mean when we say that ...

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Hint: The divergence theorem tells us that the divergence of a vector field integrated over a region $R$ with boundary $\partial R$ equals the integral of that vector field dotted with the outward-pointing normal along the boundary; \begin{align} \int_R dV\, \nabla\cdot \mathbf v=\int_{\partial R} dS\, \mathbf v\cdot\mathbf n. \end{align} If we are ...

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In a metallic conductor the most energetic conduction electrons are moving at the Fermi speed, which is surprisingly high. For example in copper it's around $10^6$ m/sec. However the electrons are continually scattering off the lattice of metal atoms so the direction of the electron motion is randomised and the average velocity relative to the lattice of ...

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The field from a current in a wire is purely magnetic for a static current. When the current varies with time, there will be radiation. What you are missing is that a radio antenna doesn't operate with DC. You can perhaps understand it like this: the magnetic field from a current loop depends on its magnetic moment, which is current times area. When the ...

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