Update 2022-02-14 06:33
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@@ -1,7 +1,7 @@
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<!DOCTYPE html>
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<html lang="en">
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<head>
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<!-- 2022-02-10 Thu 08:32 -->
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<!-- 2022-02-13 Sun 21:20 -->
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<meta charset="utf-8">
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<meta name="viewport" content="width=device-width, initial-scale=1">
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<title>Pre-Quantum Electrodynamics</title>
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@@ -1601,7 +1601,7 @@ Table of contents
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<p>
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Since \({\boldsymbol \nabla} \cdot {\bf B} = 0\) in magnetostatics, following Helmholtz's theorem we can write
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</p>
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<div class="core div" id="org51f41aa">
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<div class="core div" id="orgd9330fe">
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<p>
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\[
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{\bf B} = {\boldsymbol \nabla} \times {\bf A}
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@@ -1623,7 +1623,7 @@ add any curlless function (so gradient of a scalar field) to the vector potentia
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without changing the magnetic field. This is called a {\bf gauge choice} in electrodynamics.
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For example, we can {\bf always} eliminate the divergence of \({\bf A}\),
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</p>
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<div class="main div" id="org0c06eb5">
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<div class="main div" id="org736c1a7">
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<p>
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{\bf Example gauge choice:}
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\[
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@@ -1654,7 +1654,7 @@ zero at infinity,
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<p>
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Under this gauge choice, Ampère's law becomes
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</p>
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<div class="main div" id="org96ca0d6">
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<div class="main div" id="orgab5a943">
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<p>
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\[
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{\boldsymbol \nabla}^2 {\bf A} = -\mu_0 {\bf J}
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@@ -1667,7 +1667,7 @@ Under this gauge choice, Ampère's law becomes
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Note: this is a Poisson equation for each component.
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For currents falling off sufficiently rapidly at infinity,
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</p>
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<div class="core div" id="orgc930510">
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<div class="core div" id="org3520ab8">
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<p>
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\[
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{\bf A} ({\bf r}) = \frac{\mu_0}{4\pi} \int d\tau' \frac{J({\bf r}')}{|{\bf r} - {\bf r}'|}
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@@ -1679,7 +1679,7 @@ For currents falling off sufficiently rapidly at infinity,
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<p>
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For line and surface currents, <i>(beware Griffiths' <b>horrendous</b> notation)</i>
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</p>
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<div class="main div" id="org3af3abe">
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<div class="main div" id="orgd89f55e">
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<p>
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\[
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{\bf A}({\bf r}) = \frac{\mu_0}{4\pi} \int dl' \frac{{\bf I ({\bf r}')}}{|{\bf r} - {\bf r}'|},
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@@ -1693,7 +1693,7 @@ For line and surface currents, <i>(beware Griffiths' <b>horrendous</b> notation)
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<div class="example div" id="org9fe03ab">
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<div class="example div" id="orgc0631de">
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<p>
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\paragraph{Example 5.11:} a spherical shell of radius \(R\), carrying a uniform surface charge
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\(\sigma\), is set spinning at angular velocity \(\omega\). Find the vector potential at \({\bf r}\).
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@@ -1707,7 +1707,7 @@ the sphere is uniform !
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</div>
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<div class="example div" id="org050c6b9">
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<div class="example div" id="org0904d42">
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<p>
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\paragraph{Example 5.12:} find the vector potential of an infinite solenoid with \(n\) turns
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pet unit length, radius \(R\) and current \(I\).
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@@ -1765,6 +1765,8 @@ For an 'amperian' loop outside, the flux is always \(\mu_0 n I (\pi R^2)\), so
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<li><a href="ems_ms_vp_LC.html">The Levi-Civita Symbol</a><span class="headline-id">ems.ms.vp.LC</span></li>
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</ul>
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<br><ul class="navigation-links"><li>Prev: <a href="ems_ms_dcB_BS.html">Divergence and Curl of \({\bf B}\) from Biot-Savart <small>[ems.ms.dcB.BS]</small></a></li><li>Next: <a href="ems_ms_vp_mbc.html">Magnetic Boundary Conditions <small>[ems.ms.vp.mbc]</small></a></li><li>Up: <a href="ems_ms.html">Magnetostatics <small>[ems.ms]</small></a></li></ul>
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<br>
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<hr>
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<div class="license">
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<a rel="license noopener" href="https://creativecommons.org/licenses/by/4.0/"
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@@ -1778,7 +1780,7 @@ target="_blank">Creative Commons Attribution 4.0 International License</a>.
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</div>
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<div id="postamble" class="status">
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<p class="author">Author: Jean-Sébastien Caux</p>
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<p class="date">Created: 2022-02-10 Thu 08:32</p>
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<p class="date">Created: 2022-02-13 Sun 21:20</p>
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<p class="validation"></p>
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</div>
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