{"id":1596,"date":"2026-09-08T08:07:14","date_gmt":"2026-09-08T08:07:14","guid":{"rendered":"https:\/\/maroczain.com\/scolaire.maroczain.com\/?page_id=1596"},"modified":"2026-09-08T08:07:14","modified_gmt":"2026-09-08T08:07:14","slug":"induction-electromagnetique-cpge","status":"publish","type":"page","link":"https:\/\/maroczain.com\/scolaire.maroczain.com\/induction-electromagnetique-cpge\/","title":{"rendered":"Induction \u00e9lectromagn\u00e9tique CPGE."},"content":{"rendered":"\n&#8220;`html\n<div id=\"mza-induction-cpge\">\n\n<style>\n#mza-induction-cpge,#mza-induction-cpge *{box-sizing:border-box}\n#mza-induction-cpge{\n --navy:#06172c;--navy2:#0d416d;--gold:#c99a36;--gold2:#efd68c;\n --paper:#f5f6f8;--white:#fff;--text:#18283a;--muted:#687789;--line:#dfe5eb;\n font-family:Arial,Helvetica,sans-serif;background:var(--paper);color:var(--text);overflow:hidden\n}\n#mza-induction-cpge a{text-decoration:none;color:inherit}\n#mza-induction-cpge 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display:none;margin-top:18px;padding:20px;border-radius:14px;background:var(--navy);color:#fff\n}\n#mza-induction-cpge .cta{\n text-align:center;padding:50px 24px;border-radius:25px;\n background:linear-gradient(135deg,#06172c,#0d416d);color:#fff\n}\n#mza-induction-cpge .cta h2{color:#fff}\n#mza-induction-cpge .cta p{max-width:760px;margin:0 auto 22px;color:#cfdae4;line-height:1.7}\n\n@media(max-width:900px){\n #mza-induction-cpge .grid,\n #mza-induction-cpge .grid3,\n #mza-induction-cpge .method{grid-template-columns:1fr}\n}\n<\/style>\n\n<header class=\"hero\">\n<div class=\"wrap\">\n\n<span class=\"badge\">COURS 09 \u2022 PHYSIQUE CPGE<\/span>\n\n<h1>Flux.<br>Variation. Induction.<\/h1>\n\n<p class=\"lead\">\nL&#8217;induction \u00e9lectromagn\u00e9tique relie variation de flux magn\u00e9tique et apparition\nd&#8217;une force \u00e9lectromotrice. Faraday, Lenz, auto-induction et \u00e9nergie magn\u00e9tique\npermettent de comprendre g\u00e9n\u00e9rateurs, moteurs, transformateurs et circuits inductifs.\n<\/p>\n\n<div class=\"actions\">\n<a href=\"#cours\" class=\"btn gold\">\ud83d\udcda COMMENCER<\/a>\n<a href=\"#methode\" class=\"btn glass\">\ud83e\udde0 M\u00c9THODE<\/a>\n<a href=\"#exercices\" class=\"btn glass\">\ud83e\udde9 EXERCICES<\/a>\n<a href=\"#qcm\" class=\"btn glass\">\u2753 QCM<\/a>\n<\/div>\n\n<\/div>\n<\/header>\n\n<section id=\"cours\">\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\">1. FLUX MAGN\u00c9TIQUE<\/span>\n<h2>Mesurer le champ qui traverse une surface.<\/h2>\n<\/div>\n\n<div class=\"card\">\n\n<p>Le flux magn\u00e9tique \u00e0 travers une surface orient\u00e9e S vaut :<\/p>\n\n<div class=\"formula\">\n\u03a6 = \u222c<sub>S<\/sub> B \u00b7 dS\n<\/div>\n\n<p>\nSi B est uniforme et la surface plane :\n<\/p>\n\n<div class=\"formula\">\n\u03a6 = BS cos \u03b8\n<\/div>\n\n<p>\no\u00f9 \u03b8 est l&#8217;angle entre B et la normale \u00e0 la surface.\n<\/p>\n\n<\/div>\n<\/div>\n<\/section>\n\n<section style=\"background:#efede7\">\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\">2. LOI DE FARADAY<\/span>\n<h2>Une variation de flux cr\u00e9e une force \u00e9lectromotrice.<\/h2>\n<\/div>\n\n<div class=\"card\">\n\n<div class=\"formula\">\ne = &#8211; d\u03a6\/dt\n<\/div>\n\n<p>\nPour une bobine de N spires :\n<\/p>\n\n<div class=\"formula\">\ne = -N d\u03a6\/dt\n<\/div>\n\n<div class=\"tip\">\nL&#8217;induction appara\u00eet d\u00e8s que le flux varie, que cette variation provienne du champ, de la surface ou de l&#8217;orientation du circuit.\n<\/div>\n\n<\/div>\n<\/section>\n\n<section>\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\">3. LOI DE LENZ<\/span>\n<h2>Le signe moins a un sens physique.<\/h2>\n<\/div>\n\n<div class=\"card\">\n\n<p>\nLe courant induit s&#8217;oppose, par ses effets, \u00e0 la cause qui lui a donn\u00e9 naissance.\n<\/p>\n\n<div class=\"formula\">\ne = &#8211; d\u03a6\/dt\n<\/div>\n\n<p>\nCe principe exprime la coh\u00e9rence \u00e9nerg\u00e9tique de l&#8217;induction.\n<\/p>\n\n<div class=\"tip\">\nNe m\u00e9morisez pas seulement le signe : raisonnez sur la variation du flux et sur la r\u00e9ponse du circuit.\n<\/div>\n\n<\/div>\n<\/section>\n\n<section id=\"methode\" class=\"dark\">\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\" style=\"color:#efd68c\">MZA INDUCTION ENGINE<\/span>\n<h2>La m\u00e9thode en six r\u00e9flexes.<\/h2>\n<\/div>\n\n<div class=\"method\">\n<div><b>01<\/b><span>ORIENTATION<\/span><\/div>\n<div><b>02<\/b><span>FLUX<\/span><\/div>\n<div><b>03<\/b><span>VARIATION<\/span><\/div>\n<div><b>04<\/b><span>FARADAY<\/span><\/div>\n<div><b>05<\/b><span>LENZ<\/span><\/div>\n<div><b>06<\/b><span>\u00c9NERGIE<\/span><\/div>\n<\/div>\n\n<\/div>\n<\/section>\n\n<section>\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\">4. FEM DE MOUVEMENT<\/span>\n<h2>D\u00e9placer un conducteur dans un champ magn\u00e9tique.<\/h2>\n<\/div>\n\n<div class=\"card\">\n\n<p>\nPour une tige conductrice de longueur \u2113 se d\u00e9pla\u00e7ant \u00e0 vitesse v\nperpendiculairement \u00e0 un champ uniforme B :\n<\/p>\n\n<div class=\"formula\">\ne = B\u2113v\n<\/div>\n\n<p>\ndans la configuration simple o\u00f9 v, B et la tige sont mutuellement perpendiculaires.\n<\/p>\n\n<\/div>\n<\/section>\n\n<section style=\"background:#efede7\">\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\">5. RAILS DE LAPLACE<\/span>\n<h2>Couplage entre m\u00e9canique et \u00e9lectromagn\u00e9tisme.<\/h2>\n<\/div>\n\n<div class=\"card\">\n\n<p>\nUne barre conductrice mobile sur deux rails dans un champ B poss\u00e8de une FEM induite :\n<\/p>\n\n<div class=\"formula\">\ne = B\u2113v\n<\/div>\n\n<p>\nSi le circuit poss\u00e8de une r\u00e9sistance R :\n<\/p>\n\n<div class=\"formula\">\ni = e\/R\n<\/div>\n\n<p>\nLa barre subit ensuite une force de Laplace :\n<\/p>\n\n<div class=\"formula\">\nF = i\u2113B\n<\/div>\n\n<p>\ndont le sens s&#8217;oppose au mouvement conform\u00e9ment \u00e0 la loi de Lenz.\n<\/p>\n\n<\/div>\n<\/section>\n\n<section>\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\">6. PUISSANCE &#038; CONVERSION D&#8217;\u00c9NERGIE<\/span>\n<h2>L&#8217;induction traduit un transfert r\u00e9el.<\/h2>\n<\/div>\n\n<div class=\"grid\">\n\n<div class=\"card\">\n<h3>Puissance m\u00e9canique<\/h3>\n<div class=\"formula\">\nP<sub>m\u00e9c<\/sub> = Fv\n<\/div>\n<\/div>\n\n<div class=\"card\">\n<h3>Puissance \u00e9lectrique<\/h3>\n<div class=\"formula\">\nP<sub>\u00e9lec<\/sub> = ei\n<\/div>\n<\/div>\n\n<div class=\"card\">\n<h3>Effet Joule<\/h3>\n<div class=\"formula\">\nP<sub>J<\/sub> = Ri\u00b2\n<\/div>\n<\/div>\n\n<div class=\"card\">\n<h3>Id\u00e9e cl\u00e9<\/h3>\n<p>\nLa force induite s&#8217;oppose au mouvement car l&#8217;\u00e9nergie \u00e9lectrique produite doit provenir du travail m\u00e9canique fourni.\n<\/p>\n<\/div>\n\n<\/div>\n<\/div>\n<\/section>\n\n<section style=\"background:#efede7\">\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\">7. AUTO-INDUCTION<\/span>\n<h2>Un circuit peut s&#8217;opposer aux variations de son propre courant.<\/h2>\n<\/div>\n\n<div class=\"card\">\n\n<p>\nLe flux propre d&#8217;une bobine est souvent proportionnel au courant :\n<\/p>\n\n<div class=\"formula\">\n\u03a6<sub>propre<\/sub> = Li\n<\/div>\n\n<p>\no\u00f9 L est l&#8217;inductance.\n<\/p>\n\n<p>\nLa FEM d&#8217;auto-induction vaut :\n<\/p>\n\n<div class=\"formula\">\ne<sub>L<\/sub> = -L di\/dt\n<\/div>\n\n<\/div>\n<\/section>\n\n<section>\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\">8. INDUCTANCE<\/span>\n<h2>L&#8217;\u00e9quivalent \u00e9lectromagn\u00e9tique d&#8217;une inertie.<\/h2>\n<\/div>\n\n<div class=\"grid\">\n\n<div class=\"card\">\n<h3>Grandeur<\/h3>\n<div class=\"formula\">\nL\n<\/div>\n<\/div>\n\n<div class=\"card\">\n<h3>Unit\u00e9<\/h3>\n<div class=\"formula\">\nhenry (H)\n<\/div>\n<\/div>\n\n<div class=\"card\">\n<h3>Interpr\u00e9tation<\/h3>\n<p>\nUne grande inductance rend plus difficile une variation rapide du courant.\n<\/p>\n<\/div>\n\n<div class=\"card\">\n<h3>Analogie<\/h3>\n<p>\nL&#8217;inductance joue vis-\u00e0-vis du courant un r\u00f4le comparable \u00e0 l&#8217;inertie m\u00e9canique vis-\u00e0-vis de la vitesse.\n<\/p>\n<\/div>\n\n<\/div>\n<\/div>\n<\/section>\n\n<section style=\"background:#efede7\">\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\">9. \u00c9NERGIE MAGN\u00c9TIQUE D&#8217;UNE BOBINE<\/span>\n<h2>Stocker de l&#8217;\u00e9nergie dans le champ magn\u00e9tique.<\/h2>\n<\/div>\n\n<div class=\"card\">\n\n<div class=\"formula\">\nE<sub>m<\/sub> = \u00bdLi\u00b2\n<\/div>\n\n<p>\nCette \u00e9nergie est restituable lors de la diminution du courant.\n<\/p>\n\n<\/div>\n<\/section>\n\n<section>\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\">10. CIRCUIT RL \u2014 \u00c9TABLISSEMENT DU COURANT<\/span>\n<h2>Le courant ne s&#8217;\u00e9tablit pas instantan\u00e9ment.<\/h2>\n<\/div>\n\n<div class=\"card\">\n\n<p>\nPour une source constante E alimentant une r\u00e9sistance R et une inductance L en s\u00e9rie :\n<\/p>\n\n<div class=\"formula\">\nL di\/dt + Ri = E\n<\/div>\n\n<p>\navec i(0)=0 :\n<\/p>\n\n<div class=\"formula\">\ni(t)=E\/R \u00b7 (1-e<sup>-t\/\u03c4<\/sup>)\n<\/div>\n\n<p>\no\u00f9 :\n<\/p>\n\n<div class=\"formula\">\n\u03c4 = L\/R\n<\/div>\n\n<\/div>\n<\/section>\n\n<section style=\"background:#efede7\">\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\">11. CIRCUIT RL \u2014 D\u00c9CROISSANCE<\/span>\n<h2>La bobine maintient temporairement le courant.<\/h2>\n<\/div>\n\n<div class=\"card\">\n\n<p>\nLorsque la source est retir\u00e9e :\n<\/p>\n\n<div class=\"formula\">\nL di\/dt + Ri = 0\n<\/div>\n\n<p>\nLa solution est :\n<\/p>\n\n<div class=\"formula\">\ni(t)=I\u2080e<sup>-t\/\u03c4<\/sup>\n<\/div>\n\n<p>\navec :\n<\/p>\n\n<div class=\"formula\">\n\u03c4=L\/R\n<\/div>\n\n<\/div>\n<\/section>\n\n<section>\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\">12. CONTINUIT\u00c9 DU COURANT<\/span>\n<h2>Un courant dans une inductance id\u00e9ale ne saute pas instantan\u00e9ment.<\/h2>\n<\/div>\n\n<div class=\"card\">\n\n<p>\nComme :\n<\/p>\n\n<div class=\"formula\">\nu<sub>L<\/sub> = L di\/dt\n<\/div>\n\n<p>\nune variation instantan\u00e9e finie du courant exigerait une tension impulsionnelle id\u00e9alement infinie.\n<\/p>\n\n<div class=\"tip\">\nR\u00e9flexe CPGE : dans une bobine id\u00e9ale, i(0\u207a)=i(0\u207b).\n<\/div>\n\n<\/div>\n<\/section>\n\n<section style=\"background:#efede7\">\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\">13. INDUCTION MUTUELLE<\/span>\n<h2>Deux circuits peuvent se coupler magn\u00e9tiquement.<\/h2>\n<\/div>\n\n<div class=\"card\">\n\n<p>\nLe courant i\u2081 d&#8217;un premier circuit peut cr\u00e9er dans un second circuit un flux :\n<\/p>\n\n<div class=\"formula\">\n\u03a6\u2082\u2081 = M i\u2081\n<\/div>\n\n<p>\nLa FEM induite dans le second vaut alors :\n<\/p>\n\n<div class=\"formula\">\ne\u2082 = -M di\u2081\/dt\n<\/div>\n\n<p>\nM est l&#8217;inductance mutuelle.\n<\/p>\n\n<\/div>\n<\/section>\n\n<section>\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\">14. G\u00c9N\u00c9RATEUR \u00c9LECTROMAGN\u00c9TIQUE<\/span>\n<h2>Transformer une rotation en tension \u00e9lectrique.<\/h2>\n<\/div>\n\n<div class=\"card\">\n\n<p>\nUne spire de surface S tournant \u00e0 vitesse angulaire \u03c9 dans un champ uniforme B poss\u00e8de un flux :\n<\/p>\n\n<div class=\"formula\">\n\u03a6(t)=BS cos(\u03c9t)\n<\/div>\n\n<p>\ndonc une FEM :\n<\/p>\n\n<div class=\"formula\">\ne(t)=BS\u03c9 sin(\u03c9t)\n<\/div>\n\n<p>\nPour N spires :\n<\/p>\n\n<div class=\"formula\">\ne(t)=NBS\u03c9 sin(\u03c9t)\n<\/div>\n\n<\/div>\n<\/section>\n\n<section id=\"exercices\" style=\"background:#efede7\">\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\">15. EXERCICES PROGRESSIFS<\/span>\n<h2>Flux d&#8217;abord, Faraday ensuite.<\/h2>\n<\/div>\n\n<div class=\"exercise\">\n<span class=\"level\">NIVEAU 1<\/span>\n<h3>Exercice 1 \u2014 Surface tournante<\/h3>\n<p>\nUne spire de surface S tourne dans un champ uniforme B avec \u03b8=\u03c9t.\n\u00c9crire le flux magn\u00e9tique.\n<\/p>\n<button type=\"button\" class=\"btn gold\" onclick=\"mzaIndHint('indHint1')\">\ud83d\udca1 INDICE<\/button>\n<div id=\"indHint1\" class=\"hint\">\nLe flux d\u00e9pend du produit BS cos \u03b8.\n<\/div>\n<\/div>\n\n<div class=\"exercise\">\n<span class=\"level\">NIVEAU 2<\/span>\n<h3>Exercice 2 \u2014 FEM induite<\/h3>\n<p>\n\u00c0 partir du flux pr\u00e9c\u00e9dent, d\u00e9terminer la FEM induite.\n<\/p>\n<button type=\"button\" class=\"btn gold\" onclick=\"mzaIndHint('indHint2')\">\ud83d\udca1 INDICE<\/button>\n<div id=\"indHint2\" class=\"hint\">\nAppliquez directement e=-d\u03a6\/dt.\n<\/div>\n<\/div>\n\n<div class=\"exercise\">\n<span class=\"level\">NIVEAU 3<\/span>\n<h3>Exercice 3 \u2014 Circuit RL<\/h3>\n<p>\nUn circuit RL s\u00e9rie est aliment\u00e9 brutalement par une tension continue E.\nD\u00e9terminer le courant \u00e0 long terme et la constante de temps.\n<\/p>\n<button type=\"button\" class=\"btn gold\" onclick=\"mzaIndHint('indHint3')\">\ud83d\udca1 INDICE<\/button>\n<div id=\"indHint3\" class=\"hint\">\n\u00c0 long terme, di\/dt=0. La constante de temps vaut L\/R.\n<\/div>\n<\/div>\n\n<div class=\"exercise\">\n<span class=\"level\">NIVEAU PR\u00c9PA<\/span>\n<h3>Exercice 4 \u2014 Barre mobile<\/h3>\n<p>\nUne barre conductrice de longueur \u2113 se d\u00e9place \u00e0 vitesse v sur deux rails dans un champ B.\nLe circuit poss\u00e8de une r\u00e9sistance R. D\u00e9terminer le courant induit et la force magn\u00e9tique sur la barre.\n<\/p>\n<button type=\"button\" class=\"btn gold\" onclick=\"mzaIndHint('indHint4')\">\ud83d\udca1 INDICE<\/button>\n<div id=\"indHint4\" class=\"hint\">\nCommencez par le flux, retrouvez e=B\u2113v, puis i=e\/R et enfin la force de Laplace.\n<\/div>\n<\/div>\n\n<\/div>\n<\/section>\n\n<section>\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\">16. PROBLEM LAB<\/span>\n<h2>Mission : freinage \u00e9lectromagn\u00e9tique.<\/h2>\n<\/div>\n\n<div class=\"card\">\n\n<h3>Situation<\/h3>\n\n<p>\nUne barre conductrice de masse m et de longueur \u2113 glisse sans frottement\nsur deux rails horizontaux. Elle ferme un circuit de r\u00e9sistance R.\nL&#8217;ensemble est plong\u00e9 dans un champ magn\u00e9tique uniforme B perpendiculaire au plan.\nLa barre poss\u00e8de initialement une vitesse v\u2080.\n<\/p>\n\n<p>Votre mission :<\/p>\n\n<ol>\n<li>exprimer le flux magn\u00e9tique \u00e0 travers le circuit ;<\/li>\n<li>d\u00e9terminer la FEM induite ;<\/li>\n<li>d\u00e9terminer le courant induit ;<\/li>\n<li>trouver le sens du courant avec la loi de Lenz ;<\/li>\n<li>d\u00e9terminer la force de Laplace sur la barre ;<\/li>\n<li>montrer que cette force s&#8217;oppose au mouvement ;<\/li>\n<li>\u00e9tablir l&#8217;\u00e9quation diff\u00e9rentielle de v(t) ;<\/li>\n<li>identifier une constante de temps m\u00e9canique ;<\/li>\n<li>d\u00e9crire l&#8217;\u00e9volution de l&#8217;\u00e9nergie cin\u00e9tique ;<\/li>\n<li>relier l&#8217;\u00e9nergie perdue m\u00e9caniquement \u00e0 l&#8217;\u00e9nergie dissip\u00e9e par effet Joule.<\/li>\n<\/ol>\n\n<div class=\"actions\">\n<button type=\"button\" class=\"btn gold\" onclick=\"mzaIndHint('indMission1')\">\ud83d\udca1 INDICE<\/button>\n<button type=\"button\" class=\"btn\" style=\"background:#06172c;color:#fff\" onclick=\"mzaIndHint('indMission2')\">\ud83e\udde0 M\u00c9THODE<\/button>\n<\/div>\n\n<div id=\"indMission1\" class=\"hint\">\nSi x mesure la position de la barre, le flux est proportionnel \u00e0 B\u2113x. Sa d\u00e9riv\u00e9e introduit directement la vitesse.\n<\/div>\n\n<div id=\"indMission2\" class=\"hint\">\nEncha\u00eenez : flux \u2192 FEM \u2192 courant \u2192 force de Laplace \u2192 Newton. Vous obtiendrez une \u00e9quation diff\u00e9rentielle lin\u00e9aire du premier ordre sur v(t).\n<\/div>\n\n<\/div>\n<\/div>\n<\/section>\n\n<section class=\"dark\">\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\" style=\"color:#efd68c\">MZA FARADAY CHECK<\/span>\n<h2>Les six r\u00e9flexes de l&#8217;induction.<\/h2>\n<\/div>\n\n<div class=\"method\">\n<div><b>A<\/b><span>ORIENTATION<\/span><\/div>\n<div><b>B<\/b><span>\u03a6<\/span><\/div>\n<div><b>C<\/b><span>d\u03a6\/dt<\/span><\/div>\n<div><b>D<\/b><span>LENZ<\/span><\/div>\n<div><b>E<\/b><span>CIRCUIT<\/span><\/div>\n<div><b>F<\/b><span>\u00c9NERGIE<\/span><\/div>\n<\/div>\n\n<\/div>\n<\/section>\n\n<section id=\"qcm\">\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\">17. QCM DE VALIDATION<\/span>\n<h2>Diagnostic Induction \u00e9lectromagn\u00e9tique.<\/h2>\n<p>Le score est affich\u00e9 sans r\u00e9v\u00e9ler les r\u00e9ponses correctes.<\/p>\n<\/div>\n\n<div class=\"qcm\">\n\n<form id=\"indQuiz\">\n\n<div class=\"question\">\n<strong>1. La loi de Faraday s&#8217;\u00e9crit :<\/strong>\n<label><input type=\"radio\" name=\"i1\" value=\"1\"> e = -d\u03a6\/dt<\/label>\n<label><input type=\"radio\" name=\"i1\" value=\"0\"> e = \u03a6t<\/label>\n<label><input type=\"radio\" name=\"i1\" value=\"0\"> e = dB\/dx uniquement<\/label>\n<label><input type=\"radio\" name=\"i1\" value=\"0\"> e = Ri toujours<\/label>\n<\/div>\n\n<div class=\"question\">\n<strong>2. La loi de Lenz indique que :<\/strong>\n<label><input type=\"radio\" name=\"i2\" value=\"1\"> l&#8217;effet induit s&#8217;oppose \u00e0 la variation qui le produit<\/label>\n<label><input type=\"radio\" name=\"i2\" value=\"0\"> le courant induit augmente toujours le flux<\/label>\n<label><input type=\"radio\" name=\"i2\" value=\"0\"> le courant induit est toujours nul<\/label>\n<label><input type=\"radio\" name=\"i2\" value=\"0\"> le champ induit est toujours parall\u00e8le au champ ext\u00e9rieur<\/label>\n<\/div>\n\n<div class=\"question\">\n<strong>3. L&#8217;\u00e9nergie stock\u00e9e dans une inductance id\u00e9ale vaut :<\/strong>\n<label><input type=\"radio\" name=\"i3\" value=\"1\"> \u00bdLi\u00b2<\/label>\n<label><input type=\"radio\" name=\"i3\" value=\"0\"> Li<\/label>\n<label><input type=\"radio\" name=\"i3\" value=\"0\"> \u00bdRi\u00b2<\/label>\n<label><input type=\"radio\" name=\"i3\" value=\"0\"> L\/i<\/label>\n<\/div>\n\n<div class=\"question\">\n<strong>4. La constante de temps d&#8217;un circuit RL s\u00e9rie vaut :<\/strong>\n<label><input type=\"radio\" name=\"i4\" value=\"1\"> L\/R<\/label>\n<label><input type=\"radio\" name=\"i4\" value=\"0\"> R\/L<\/label>\n<label><input type=\"radio\" name=\"i4\" value=\"0\"> LR<\/label>\n<label><input type=\"radio\" name=\"i4\" value=\"0\"> 1\/LR<\/label>\n<\/div>\n\n<div class=\"question\">\n<strong>5. Dans une inductance id\u00e9ale :<\/strong>\n<label><input type=\"radio\" name=\"i5\" value=\"1\"> le courant est continu lors d&#8217;une commutation ordinaire<\/label>\n<label><input type=\"radio\" name=\"i5\" value=\"0\"> le courant saute toujours instantan\u00e9ment<\/label>\n<label><input type=\"radio\" name=\"i5\" value=\"0\"> la tension est toujours nulle<\/label>\n<label><input type=\"radio\" name=\"i5\" value=\"0\"> aucune \u00e9nergie n&#8217;est stock\u00e9e<\/label>\n<\/div>\n\n<div class=\"question\">\n<strong>6. Dans une barre conductrice frein\u00e9e par induction :<\/strong>\n<label><input type=\"radio\" name=\"i6\" value=\"1\"> la force induite s&#8217;oppose au mouvement<\/label>\n<label><input type=\"radio\" name=\"i6\" value=\"0\"> la force acc\u00e9l\u00e8re toujours la barre<\/label>\n<label><input type=\"radio\" name=\"i6\" value=\"0\"> aucun courant n&#8217;appara\u00eet<\/label>\n<label><input type=\"radio\" name=\"i6\" value=\"0\"> l&#8217;\u00e9nergie m\u00e9canique augmente spontan\u00e9ment<\/label>\n<\/div>\n\n<button type=\"button\" class=\"btn gold\" onclick=\"mzaIndScore()\">\nVALIDER MON QCM\n<\/button>\n\n<\/form>\n\n<div id=\"indResult\"><\/div>\n\n<\/div>\n<\/div>\n<\/section>\n\n<section>\n<div class=\"wrap\">\n\n<div class=\"cta\">\n\n<div style=\"font-size:43px\">e = \u2212d\u03a6\/dt<\/div>\n\n<h2>L&#8217;induction transforme une variation de champ en tension \u00e9lectrique.<\/h2>\n\n<p>\nFlux, Faraday, Lenz, auto-induction et \u00e9nergie magn\u00e9tique forment le pont\nentre m\u00e9canique, circuits \u00e9lectriques et \u00e9lectromagn\u00e9tisme. Ce chapitre pr\u00e9pare\ndirectement l&#8217;\u00e9tude des circuits, des ondes et des syst\u00e8mes \u00e9lectromagn\u00e9tiques avanc\u00e9s.\n<\/p>\n\n<div class=\"actions\" style=\"justify-content:center\">\n<a href=\"#cours\" class=\"btn gold\">\ud83d\udcda REVOIR LE COURS<\/a>\n<a href=\"#exercices\" class=\"btn glass\">\ud83e\udde9 EXERCICES<\/a>\n<a href=\"#qcm\" class=\"btn glass\">\u2753 REFAIRE LE QCM<\/a>\n<\/div>\n\n<\/div>\n<\/div>\n<\/section>\n\n<script>\nfunction mzaIndHint(id){\n const el=document.getElementById(id);\n if(!el)return;\n el.style.display = el.style.display===\"block\" ? \"none\" : \"block\";\n}\n\nfunction mzaIndScore(){\n const form=document.getElementById(\"indQuiz\");\n const result=document.getElementById(\"indResult\");\n\n let score=0;\n let complete=true;\n\n [\"i1\",\"i2\",\"i3\",\"i4\",\"i5\",\"i6\"].forEach(function(name){\n   const answer=form.querySelector('input[name=\"'+name+'\"]:checked');\n   if(!answer){\n     complete=false;\n   }else{\n     score+=Number(answer.value);\n   }\n });\n\n result.style.display=\"block\";\n\n if(!complete){\n   result.innerHTML=\"<strong>R\u00e9pondez aux 6 questions avant de valider.<\/strong>\";\n   return;\n }\n\n const pct=Math.round(score\/6*100);\n\n let level=\"Induction \u00e0 consolider\";\n if(pct>=50) level=\"Fondations acquises\";\n if(pct>=67) level=\"Bon niveau\";\n if(pct>=84) level=\"Tr\u00e8s bonne ma\u00eetrise\";\n if(pct===100) level=\"Excellent niveau CPGE\";\n\n result.innerHTML=\n \"<strong style='font-size:30px;color:#efd68c'>\"+pct+\"%<\/strong>\"+\n \"<p><b>\"+level+\"<\/b><\/p>\"+\n \"<p>Score : \"+score+\" \/ 6<\/p>\"+\n \"<p>Les r\u00e9ponses correctes et la correction d\u00e9taill\u00e9e restent masqu\u00e9es.<\/p>\";\n}\n<\/script>\n\n<\/div>\n&#8220;`\n","protected":false},"excerpt":{"rendered":"<p>&#8220;`html COURS 09 \u2022 PHYSIQUE CPGE Flux.Variation. Induction. L&#8217;induction \u00e9lectromagn\u00e9tique relie variation de flux magn\u00e9tique et apparition d&#8217;une force \u00e9lectromotrice. Faraday, Lenz, auto-induction et \u00e9nergie magn\u00e9tique permettent de comprendre g\u00e9n\u00e9rateurs, moteurs, transformateurs et circuits inductifs. \ud83d\udcda COMMENCER \ud83e\udde0 M\u00c9THODE \ud83e\udde9 EXERCICES \u2753 QCM 1. FLUX MAGN\u00c9TIQUE Mesurer le champ qui traverse une surface. Le flux [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-1596","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/maroczain.com\/scolaire.maroczain.com\/wp-json\/wp\/v2\/pages\/1596","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/maroczain.com\/scolaire.maroczain.com\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/maroczain.com\/scolaire.maroczain.com\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/maroczain.com\/scolaire.maroczain.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/maroczain.com\/scolaire.maroczain.com\/wp-json\/wp\/v2\/comments?post=1596"}],"version-history":[{"count":1,"href":"https:\/\/maroczain.com\/scolaire.maroczain.com\/wp-json\/wp\/v2\/pages\/1596\/revisions"}],"predecessor-version":[{"id":1598,"href":"https:\/\/maroczain.com\/scolaire.maroczain.com\/wp-json\/wp\/v2\/pages\/1596\/revisions\/1598"}],"wp:attachment":[{"href":"https:\/\/maroczain.com\/scolaire.maroczain.com\/wp-json\/wp\/v2\/media?parent=1596"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}