الفيزياء العامة الجزء الثاني#موقع الفيزياء.كوم

Direct Current Circuits
Example 8.14
The circuit has been connected as shown in figure 8.23 for a long time. (a)
What is the voltage across the capacitor? (b) If the battery is disconnected,
how long does it take for the capacitor to discharge to 1/10 of its initial
voltage? The capacitance C=1µF.
1Ω
c
8Ω
10V
b
a
4Ω
2Ω
d
Figure 8.23
Solution
After long time the capacitor would be fully charged and the current in the
branch ab equal zero.
The resistors in the left hand (1Ω, and 4Ω) are connected in series and
assume the current in this branch cbd is I 1 . The resistors in the right hand
(8Ω, and 2Ω) are connected in series and assume the current in this branch
cad is I 2 .
The potential difference across the points c and d is the same as the emf =
10volt. Therefore,
I = 10
10
1
= 2A
I 1
1+
4
2 8
A
2
= =
+
The total current,
I = I 1 + I 2 = 3A
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