المدة الزمنية : ساعة ونصف
النقطة المحصل عليها :

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الاسم الكامل :....................................................................
المؤسسة :...........................................................................
النيابة :......................................المدينة:..............................
الهاتف :................................................................................
البريد الإلكتروني :..............................................................	الجمعية المغربية لأساتذة العلوم الفيزيائية 	

	
1 / 3

تمرين(1) فيزياء:

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r =100Ω

A

B

1 ـ يمثل الشكل أسفله شبكة لمقاومات الكهربائية مماثلة r . علما أن كل رابطة بين عقدتين تمثل مقاومة r.أحسب المقاومة المكافئة RAB  بين النقطتين A و B.

RAB

2

1

C

C

E

2 ـ ندمج المقاومة RAB  السابقة في الدارة الكهربائية الممثلة أسفله :

q2

نعطي :  E=100V
          RAB=150Ω  
       C=1μF             

نعتبر المكثفين غير مشحونين. نضع قاطع التيار في الموضع1 ثم نؤرجه بعد ذلك نحو الموضع2 عند لحظة t=o نعتبرها أصلا للتواريخ.
1 ـ ماقيمة الشحنة 2q خلال المدة 0,1ms ؟
2 ـ أحسب الطاقة المبددة بمفعول جول في المقاومة RAB  عند نهاية الشحن.

الأجوبة

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2 / 3	الإسم الكامل : ....................................	

	
تمرين(2) فيزياء:

يعتبر اليود المادة الأساسية لتركيب هرمونات الغدة الدرقية حيث تستنزفه هذه الأخيرة من الدم وهذا الهرمون أساسي للنمو. كميات اليود اللازمة لهذا التركيب قليلة. بالنسبة لشخص عادي يحتوي كل   من الدم على  من اليود، في كل لحظة تأخذ الغدة الدرقية نفس الكمية من الدم على شكل يدور والذي تفرزه على شكل هرمونات. كميات اليود المتواجدة في الدم تبقى ثابتة. باستعمال اليود المشع يمكن تتبع استقلاب  اليود وقياس الهرمونات المركبة.
من بين نظائر اليود نجد  و  ، أحدهما مستقر والآخر باعث ل  .
1 ـ أحسب طاقة الربط ب    ثم ب    لكل من النظيرين.
2 ـ ما الطاقة اللازم إعطائها لكل نواة ساكنة لكي يتم تفكيكها إلى أيونات؟
3 ـ حدد النظير المستقر معللا جوابك.
4 ـ 
4.1 ـ أكتب معادلة تفتت النظير المشع علما أن النواة المتولدة هي  .
4.2 ـ يساوي عمر النصف لليود المشع ، استنتج ثابتة الزمن τ لليود المشع.
5 ـ
5.1 ـ أحسب نشاط  1g من    علما أن الفحص بالأحماض (scintigraphie) للغدد الدرقية 
 (glandes surrénales)يستلزم محلول لليود   نشاطه  الإشعاعي   .
5.2 ـ ماكتلة اليود التي تم حقنها؟

معطيات :      
       C=3.108m.s-1        1MeV=1,6-13J          NA=6,02.1023mol-1        M(131I)=131g.mol-1            

الأجوبة

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3 / 3 	الإسم الكامل : .................................................................	

	

ـ محلول تجاري لحمض البر ومدريك  HBr
ـ النسبة المائوية الكتلية p= 46%   
ـ الكثافة 1,46 

تمرين (3) الكيمياء:

تحمل لصيقة محلول تجاري المعلومات التالية:

علما أن حمض البر ومدريك يتفكك كليا في الماء(حمض قوي)
1 ـ تحقق أن التركيز C  للمحلول يساوي8,29 mol.L-1 
2 ـ احسب تراكيز الأنواع الكيميائية الموجودة في المحلول.
3 ـ هل يمكن حساب pH  المحلول باستعمال العلاقة pH=-log(H3O+)؟
4 ـ نريد التأكد من قيمة التركيز C للمحلول التجاري بالمعايرة، لذلك نخفف حجما من هذا المحلول 100 مرة، بواسطة محلول لهيدروكسيد الصوديوم  تركيزه cB=0,1mol.L-1 ،نعاير حجما VA=20mL ، يتطلب التكافؤ إضافة الحجم VB=16,7mL .
4.1 ـأكتب معادلة التفاعل الحاصل أثناء المعايرة.
4.2 ـ أحسب قيمة C .
      نعطي: M(Br)=80g.moL-1            ;             M(H)=1 g.moL-1        ;        ρeau=1000g/L         

الأجوبة

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