أرجو من الدكتور حازم سكيك مساعدتي في هذه الأسئلة لما رأيت فيها من الصعوبة ! ضروري

أريد حلها كي أعرف طريقة الحل و من ثم أحل المسائل الشبيهة




ضروري يا دكتور أريد الحل غفر الله لوالديك :) .




"1"
Consider the circuit shown in Figure P26.23, where C1= 6μF, C2= 3μF, and ∆V =20V .Capacitor C1 is first charged by closing of switch S1.Switch
S1 is then opened, and the charged capacitor is connected
to the uncharged capacitor by the closing of S2 .
Calculate the initial charge acquired by C1 and the final
charge on each.




"2"


Find the equivalent capacitance between points a and b
for the group of capacitors connected as shown in Figure
P26.28 if C1 = 5μf, C2 = 10μF, and C3 =2μ.


For the network described in the previous problem if
the potential difference between points a and b is
60V what charge is stored on C3?








"3"
A parallel-plate capacitor is constructed using three
dielectric materials, as shown in Figure P26.58. You may
assume that ℓ≫d.(a)Find an expression for the capacitance of the device in terms of the plate area A and d,K1,K2 and K3. (b)Calculate the capacitance using values A = 1cm^2, d= 2mm, K1 = 4.9, K2 =5.6 and K3 =2.1






"4"


A vertical parallel-plate capacitor is half filled with a dielectric
for which the dielectric constant is 2.00 (Fig.
P26.71a). When this capacitor is positioned horizontally,
what fraction of it should be filled with the same
dielectric (Fig. P26.71b) so that the two capacitors have
equal capacitance?











"5"


a)How much charge is on each plate of a 4μF capacitor
when it is connected to a 12.0-V battery?


(b) If this same capacitor is connected to a 1.50-V battery,
what charge is stored?














"6"


Two conductor having net charges of +10μC and -10μC have a potential difference of 10.0 V. Determine
(a) the capacitance of the system and (b) the potential
difference between the two conductors if the charges
on each are increased to +100μC and -100μC.










"7"


Explain why the work needed to move a charge Q through a potential difference ∆V is W=Q∆V , whereas the energy stored in a charged capacitor is U=½Q∆V
Where does the ½ factor come from ?




"8"


If the potential difference across a capacitor is doubled,
by what factor does the stored energy change?


"9"


Why is it dangerous to touch the terminals of a highvoltage
capacitor even after the applied voltage has been
turned off? What can be done to make the capacitor safe
to handle after the voltage source has been removed?




"10"
Explain why a dielectric increases the maximum operating
voltage of a capacitor even though the physical size of
the capacitor does not change






"11"


Because the net charge in a capacitor is always zero, what
does a capacitor store?




"12"
Because the charges on the plates of a parallel-plate capacitor
are of opposite sign, they attract each other.
Hence, it would take positive work to increase the plate
separation. What happens to the external work done in
this process?


"13"
An isolated charged conducting sphere of radius
12cm creates an electric field of 4.9 ×10^4 N/C at a distance 21cm from its center. (a) What is its surface charge density ?(b)What is its capacitance?






"14"




Two conducting spheres with diameters of 0.400 m and
1.00m are separated by a distance that is large compared
with the diameters. The spheres are connected by
a thin wire and are charged to 7μC.(a) How is this total charge shared between the spheres? (Neglect any charge on the wire.)(b)What is the potential of the system of spheres when the reference potential is taken to be V=0 at r=∞?









"15"




Two capacitors C1= 5μF and C2 = 12μF are connected in parallel, and the resulting combination is connected to a 9V battery,
(a) What is the value of the
equivalent capacitance of the combination? What are
(b) the potential difference across each capacitor and
(c) the charge stored on each capacitor?












"16"


The inner conductor of a coaxial cable has a radius of
0.800 mm, and the outer conductor’s inside radius is
3.00 mm. The space between the conductors is filled
with polyethylene, which has a dielectric constant of 2.3
6-^10×18 and a dielectric strength of
V/m. What is the maximum potential difference that this cable can withstand?






كم يجب أن تكون مساحة اللوح في مكثف سعته 12μC إذا كان هناك غشاء من أكسيد الألومنيوم سمكه 20nm يملأ الفجوة بين لوحيه المتوازيين؟ اعتبر K=8 بالنسبة لأكسيد الألومنيوم .






شحن مكثف هوائي متوازي اللوحين إلى أن أصبح فرق الجهد بين لوحيه 120V ثم فصل عن البطارية . و عندمـا ملء الحيز بين اللوحين تمامـاً بقطعة من الزجاج فإن الجهد عبر المكثف هبط إلى 30V . ما هو ثابت عزل الزجاج ؟






تحدث شرارة إذا زادت شدة المجال الكهربائي عن نحو 6^10 × 3 V/m . ما مقدار الشحنة التي توضع على مكثف متوارزي اللوحين سعته 30pF و يوجد هواء بين لوحيه قبل أن تحدث الشرارة ؟ اعتبر مساحة كل من اللوحين 30cm^2 .














شحن مكثفان أحدهما سعته4μC و الآخر سعته 6μC على انفراد حتى فرق جهد مقداره 100V و ذلك بتوصيلهما كل على حدة بالبطارية. و بعد أن فصلا عن البطارية وصل الطرف الموجب لأحدهما باللوح الموجب لآخر و اللوح السالب لأحدهما باللوح السالب لآخر. أوجد (أ) الجهد عبر كل من المكثفين ؛ (ب) الشحنة النهائية على كل من المكثفين.
تلميح : بعد فصل المكثفين يكون فرق الجهد عبر كل منهما هو نفسه .


أعد المسألة السابقة و لكن عند توصيل اللوح الموجب لأحد المكثفين باللوح السالب للمكثف الآخر .








مكثف متوازي اللوحين تبلغ مساحة كل من لوحيه 4cm^2 و تفصلهما مسافة مقدارها 0.5mm . ملئ الحيز بين اللوحين بمادة ثابت عزلها K = 8 . فإذا وصلت بطارية قوتها 12V بالمكثف فكم من الطاقة سوف يختزن؟ ما هو المعامل الذي سيتغير به مقدار الشحنة المختزنة إذا أزيل العازل و ملئ الحيز بين اللوحين بالهواء بنما ظلت البطارية متصلة بالمكثف ؟




الصور :

http://img52.imageshack.us/img52/7456/figurep2623.png Figure P26.23


http://img560.imageshack.us/img560/9875/figurep2628.png Figure P26.28


http://img14.imageshack.us/img14/3376/figurep2658.png Figure P26.58


http://img12.imageshack.us/img12/9210/figurep2671.png Figure 26.71