74. ח.4.3
من التعبير عن ظل الزاوية كدالة للتيار
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تعبير الميل هو:
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نأخذ نقطتين على خط الاتجاه ونحسب قيمة الميل حسب النقطتين:

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سنقارن قيمة الميل بتعبير الميل ونحسب قيمة المركب الأفقي للحقل المغناطيسي للكرة الأرضية:
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ولذلك فإن مركب الحقل المغناطيسي الأفقي للحقل المغناطيسي للكرة الأرضية في النقطة التي توجد فيها البوصلة يساوي 33.31 ميكروتسلا.