Update 2022-03-07 20:40
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-30
@@ -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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<!-- 2022-03-02 Wed 15:45 -->
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<!-- 2022-03-07 Mon 20:38 -->
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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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@@ -1098,14 +1098,6 @@ Table of contents
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<li>
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<a href="./emdm_emwm_refl_oi.html#emdm_emwm_refl_oi">Oblique Incidence</a><span class="headline-id">emdm.emwm.refl.oi</span>
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</li>
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<li>
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<a href="./emdm_emwm_refl_Fe.html#emdm_emwm_refl_Fe">Fresnel's Equations</a><span class="headline-id">emdm.emwm.refl.Fe</span>
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</li>
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<li>
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<a href="./emdm_emwm_refl_Ba.html#emdm_emwm_refl_Ba">Brewster's Angle</a><span class="headline-id">emdm.emwm.refl.Ba</span>
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</li>
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</ul>
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@@ -1645,14 +1637,14 @@ done by EM forces? From Lorentz force law:
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Really, we're looking at a small volume element \(d\tau\) carrying charge \(\rho d\tau\), moving
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at velocity \({\bf v}\) such that \({\bf J} = \rho {\bf v}\). Thus,
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</p>
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<div class="eqlabel" id="org0197499">
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<div class="eqlabel" id="orgc9958b2">
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<p>
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<a id="dWdt_intEJ"></a><a href="./emd_ce_poy.html#dWdt_intEJ"><svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" class="bi bi-link" viewBox="0 0 16 16">
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<path d="M6.354 5.5H4a3 3 0 0 0 0 6h3a3 3 0 0 0 2.83-4H9c-.086 0-.17.01-.25.031A2 2 0 0 1 7 10.5H4a2 2 0 1 1 0-4h1.535c.218-.376.495-.714.82-1z"/>
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<path d="M9 5.5a3 3 0 0 0-2.83 4h1.098A2 2 0 0 1 9 6.5h3a2 2 0 1 1 0 4h-1.535a4.02 4.02 0 0 1-.82 1H12a3 3 0 1 0 0-6H9z"/>
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</svg></a>
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</p>
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<div class="alteqlabels" id="org9aacea3">
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<div class="alteqlabels" id="orgf9bbccb">
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<ul class="org-ul">
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<li>Gr (8.6)</li>
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</ul>
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@@ -1665,7 +1657,7 @@ at velocity \({\bf v}\) such that \({\bf J} = \rho {\bf v}\). Thus,
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\frac{dW}{dt} = \int_{\cal V} d\tau ~ {\bf E} \cdot {\bf J}
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\tag{dWdt_intEJ}\label{dWdt_intEJ}
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\]
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The integrand is the work done per unit time, per unit volume, {\it i.e.} the power delivered per unit volume.
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The integrand is the work done per unit time, per unit volume, <i>i.e.</i> the power delivered per unit volume.
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In terms of fields alone: use Ampère-Maxwell:
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\[
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{\bf E} \cdot {\bf J} = \frac{1}{\mu_0} {\bf E} \cdot ({\boldsymbol \nabla} \times {\bf B}) - \varepsilon_0 {\bf E} \cdot \frac{\partial {\bf E}}{\partial t}
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@@ -1692,18 +1684,18 @@ so we get
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Substituting this in <a href="./emd_ce_poy.html#dWdt_intEJ">dWdt_intEJ</a> and using the divergence theorem,
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we obtain
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</p>
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<div class="main div" id="orgf118f4f">
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<div class="main div" id="orgead023b">
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<p>
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<b>Poynting's theorem</b>
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</p>
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<div class="eqlabel" id="org1b7cdac">
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<div class="eqlabel" id="org1b1ef48">
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<p>
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<a id="👉Thm"></a><a href="./emd_ce_poy.html#👉Thm"><svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" class="bi bi-link" viewBox="0 0 16 16">
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<path d="M6.354 5.5H4a3 3 0 0 0 0 6h3a3 3 0 0 0 2.83-4H9c-.086 0-.17.01-.25.031A2 2 0 0 1 7 10.5H4a2 2 0 1 1 0-4h1.535c.218-.376.495-.714.82-1z"/>
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<path d="M9 5.5a3 3 0 0 0-2.83 4h1.098A2 2 0 0 1 9 6.5h3a2 2 0 1 1 0 4h-1.535a4.02 4.02 0 0 1-.82 1H12a3 3 0 1 0 0-6H9z"/>
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</svg></a>
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</p>
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<div class="alteqlabels" id="orgd7b6cac">
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<div class="alteqlabels" id="org9c51283">
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<ul class="org-ul">
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<li>Gr (8.9)</li>
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</ul>
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@@ -1729,18 +1721,18 @@ energy is carried by EM fields out of \({\cal V}\) across its boundary surface.
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<p>
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Energy per unit time, per unit area carried by EM fields: given by the
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</p>
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<div class="core div" id="orgf3198a5">
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<div class="core div" id="orgafa4bdd">
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<p>
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<b>Poynting vector</b>
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</p>
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<div class="eqlabel" id="org8725431">
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<div class="eqlabel" id="org0aaf227">
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<p>
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<a id="PoyntingVec"></a><a href="./emd_ce_poy.html#PoyntingVec"><svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" class="bi bi-link" viewBox="0 0 16 16">
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<path d="M6.354 5.5H4a3 3 0 0 0 0 6h3a3 3 0 0 0 2.83-4H9c-.086 0-.17.01-.25.031A2 2 0 0 1 7 10.5H4a2 2 0 1 1 0-4h1.535c.218-.376.495-.714.82-1z"/>
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<path d="M9 5.5a3 3 0 0 0-2.83 4h1.098A2 2 0 0 1 9 6.5h3a2 2 0 1 1 0 4h-1.535a4.02 4.02 0 0 1-.82 1H12a3 3 0 1 0 0-6H9z"/>
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</svg></a>
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</p>
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<div class="alteqlabels" id="org6f2879d">
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<div class="alteqlabels" id="org05edf23">
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<ul class="org-ul">
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<li>Gr (8.10)</li>
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</ul>
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@@ -1759,18 +1751,18 @@ Energy per unit time, per unit area carried by EM fields: given by the
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<p>
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We can thus express Poynting's theorem more compactly:
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</p>
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<div class="core div" id="org3a4bb91">
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<div class="core div" id="orgf7b3c73">
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<p>
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<b>Poynting's theorem</b> (integral form)
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</p>
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<div class="eqlabel" id="orgbf2cc63">
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<div class="eqlabel" id="org610ce5e">
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<p>
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<a id="PoyntingThm_int"></a><a href="./emd_ce_poy.html#PoyntingThm_int"><svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" class="bi bi-link" viewBox="0 0 16 16">
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<path d="M6.354 5.5H4a3 3 0 0 0 0 6h3a3 3 0 0 0 2.83-4H9c-.086 0-.17.01-.25.031A2 2 0 0 1 7 10.5H4a2 2 0 1 1 0-4h1.535c.218-.376.495-.714.82-1z"/>
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<path d="M9 5.5a3 3 0 0 0-2.83 4h1.098A2 2 0 0 1 9 6.5h3a2 2 0 1 1 0 4h-1.535a4.02 4.02 0 0 1-.82 1H12a3 3 0 1 0 0-6H9z"/>
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</svg></a>
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</p>
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<div class="alteqlabels" id="org5f484e3">
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<div class="alteqlabels" id="org462a7a9">
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<ul class="org-ul">
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<li>Gr (8.11)</li>
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</ul>
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@@ -1789,18 +1781,18 @@ We can thus express Poynting's theorem more compactly:
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<p>
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where we have defined the total
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</p>
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<div class="core div" id="orgbc7eb16">
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<div class="core div" id="org49394fc">
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<p>
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<b>Energy in electromagnetic fields</b>
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</p>
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<div class="eqlabel" id="org89872c3">
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<div class="eqlabel" id="org2fd18f3">
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<p>
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<a id="Uem"></a><a href="./emd_ce_poy.html#Uem"><svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" class="bi bi-link" viewBox="0 0 16 16">
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<path d="M6.354 5.5H4a3 3 0 0 0 0 6h3a3 3 0 0 0 2.83-4H9c-.086 0-.17.01-.25.031A2 2 0 0 1 7 10.5H4a2 2 0 1 1 0-4h1.535c.218-.376.495-.714.82-1z"/>
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<path d="M9 5.5a3 3 0 0 0-2.83 4h1.098A2 2 0 0 1 9 6.5h3a2 2 0 1 1 0 4h-1.535a4.02 4.02 0 0 1-.82 1H12a3 3 0 1 0 0-6H9z"/>
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</svg></a>
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</p>
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<div class="alteqlabels" id="org67613ca">
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<div class="alteqlabels" id="orge0e6bd0">
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<ul class="org-ul">
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<li>Gr (8.5)</li>
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</ul>
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@@ -1829,18 +1821,18 @@ Then,
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\]
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so we get the
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</p>
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<div class="core div" id="org487db23">
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<div class="core div" id="orgb7f6aa8">
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<p>
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<b>Poynting theorem</b> (differential form)
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</p>
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<div class="eqlabel" id="org9593699">
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<div class="eqlabel" id="orgc43f9ba">
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<p>
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<a id="PoyntingThm"></a><a href="./emd_ce_poy.html#PoyntingThm"><svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" class="bi bi-link" viewBox="0 0 16 16">
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<path d="M6.354 5.5H4a3 3 0 0 0 0 6h3a3 3 0 0 0 2.83-4H9c-.086 0-.17.01-.25.031A2 2 0 0 1 7 10.5H4a2 2 0 1 1 0-4h1.535c.218-.376.495-.714.82-1z"/>
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<path d="M9 5.5a3 3 0 0 0-2.83 4h1.098A2 2 0 0 1 9 6.5h3a2 2 0 1 1 0 4h-1.535a4.02 4.02 0 0 1-.82 1H12a3 3 0 1 0 0-6H9z"/>
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</svg></a>
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</p>
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<div class="alteqlabels" id="org129becb">
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<div class="alteqlabels" id="org50e67b6">
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<ul class="org-ul">
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<li>Gr (8.14)</li>
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</ul>
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@@ -1863,7 +1855,7 @@ and has a similar for to the continuity equation
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<div class="example div" id="orgd9e0ab5">
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<div class="example div" id="org76ab6ea">
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<p>
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<b>Example: Joule heating</b>
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</p>
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@@ -1895,7 +1887,7 @@ and points radially inwards. Energy per unit time passing surface of wire:
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\[
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\int d{\bf a} \cdot {\bf S} = S (2\pi a L) = -V I
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\]
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where the minus sign means energy is flowing {\it in} (the wire heats up),
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where the minus sign means energy is flowing <i>in</i> (the wire heats up),
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and the value is as expected.
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</p>
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@@ -1920,7 +1912,7 @@ 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: 2022-03-02 Wed 15:45</p>
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<p class="date">Created: 2022-03-07 Mon 20:38</p>
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<p class="validation"></p>
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</div>
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