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If there is a changing charge density, then there must be accelerating charges somewhere. As an example of this, suppose we have two small conducting spheres separated by a distance $l$ and connected ...
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An infinitely small dipole in the form $$\rho = \vec{P} \cdot \nabla \delta^3(r)$$ Will only have an acceleration/ changing current density/ radiation given: $$\frac{d^2\vec{P}}{dt^2} ≠ 0$$ The reason ...
• 5,235
1 vote

### How a dipole should behave in order to produce an electromagnetic field?

Suppose you have a dipole moment consisting of two charges $\pm q$ and the length between them is $d$. But now suppose that the charge at "each end" of the dipole is time dependent such that ...
• 113k
1 vote
Accepted

### How a dipole should behave in order to produce an electromagnetic field?

As long as the dipole moment (a vector quantity) oscillates, the system radiates. If you know how the dipole moment changes with time, that's enough. The reason why the dipole moment changes doesn't ...
• 4,765
1 vote

### How a dipole should behave in order to produce an electromagnetic field?

Suppose you had a dipole with a constant distance d between the equal charges, and the dipole rotated. Then the charges would be accelerated and it would produce EM waves. The EM waves would be ...
• 2,421

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