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I have the following expression of oscillating dipole, $$d = \vec{d}_0\sin(\omega t).$$ Find the strength of the magnetic field, $$\vec{H} = \,?$$

My solution at the moment: $$\vec{A} = \frac{\vec{d}(t-\frac{r}{c})}{r c}$$ $$\varphi = \frac{\vec{d}(t-\frac{r}{c})\cdot\vec{r}}{r^3}$$ $$\vec{H}=\operatorname{rot}\vec{A}$$ $$\vec{E} = -\frac{1}{c}\frac{\partial \vec{A}}{\partial t}-\operatorname{grad}\varphi$$ $$\vec{A} = \frac{\vec{d}_0\sin\left[\omega(t-\frac{r}{c})\right]}{rc} $$ $$ \vec{H} = \operatorname{rot}{\vec{A}}= \begin{bmatrix} \vec{\imath} & \vec{\jmath} & \vec{k} \\ \frac{\partial}{\partial x} & \frac{\partial}{\partial y} & \frac{\partial}{\partial z} \\ A_x & A_y & A_z \end{bmatrix} = \vec{\imath}\left(\frac{\partial}{\partial y}A_z-\frac{\partial}{\partial z}A_y\right) + \vec{\jmath}\left(\frac{\partial}{\partial z}A_x-\frac{\partial}{\partial x}A_z\right) + \vec{k}\left(\frac{\partial}{\partial x}A_y-\frac{\partial}{\partial y}A_x\right) = (*) $$

How do we find $A_x$, $A_y$, and $A_z$, as we don’t have any $x$, $y$, or $z$ here? Am I missing vector above any of $r$? If yes, where exactly and what to do next?

My tutor once told me that $r$ is something like a square root of sum $x^2+y^2+z^2$? Is that true?

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    $\begingroup$ Regarding your flag on this post, you can edit your post for yourself using the "Edit" button under the post. $\endgroup$
    – Chris
    Commented Apr 21, 2022 at 22:59
  • $\begingroup$ I believe you are on the right path. You need to extract the vector potential from the dipole, and you'll need to use the retard potential as well. Where you might be getting stuck is the coordinate frame to use. Can you assume that $\vec{d}$ is pointing in the "z-hat" direction, used in cylindrical coordinates? That should make the cross-product a lot easier to work out. I can give you a reference to look-up the answer, but wanted to help you work it out on your own, before hand. $\endgroup$
    – tau1777
    Commented Apr 22, 2022 at 0:06
  • $\begingroup$ @tau1777 Probably d isn't in spherical or cylindrical coords. $\endgroup$
    – Oleg
    Commented Apr 22, 2022 at 0:21
  • $\begingroup$ @tau1777 I've got the following for the A: $\vec{A} = \frac{(d0_x \vec{i} + d0_y \vec{j} + d0_z \vec{k}) \sin{(\omega(t-\frac{\sqrt{x^2 + y^2 + z^2}}{c}))}}{c\sqrt{x^2 + y^2 + z^2}}$ $\endgroup$
    – Oleg
    Commented Apr 22, 2022 at 0:23
  • $\begingroup$ Yes, I think that is correct, it could be that what I'm looking at is choosing the dipole vector to point along z-hat. So if you went to cylindrical coordinates and made that simplifying assumptions, that would be exact what my book has, with some constants out in front. I would check if you can make that assumption or not, I think the dipole should be pointed along one-axis, so it isn't a large assumption, but check. If you can, it will make taking the cross product a lot simpler. $\endgroup$
    – tau1777
    Commented Apr 22, 2022 at 0:35

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