الفيزياء العامة الجزء الثاني#موقع الفيزياء.كوم

The potential difference across the capacitor V b -V a is
V b -V a = 8I 2 - 1I 1 = 8 × 1 - 1 × 2 = 6volt
Lectures in General Physics
To find the answer of (b) we need to find the equivalent resistance,
1
R
=
1
R
1
1
+
R
2
=
1
5
+
1
10
=
3
10
Where R 1 is the equivalent resistance for (1Ω, and 4Ω), and R 2 is the
equivalent resistance for (2Ω, and 8Ω)
R=3.3Ω
From equation 8.17
q = Qe
−t
RC
Divide by the capacitance C, therefore
q
C
=
Q
C
e
−t
RC
v = Ve
−t
RC
∴
v
V
= e
−t
RC
The time for the capacitor to discharge to 1/10 of its initial voltage
1
10
= e −t
RC
Ln1 - Ln10 = -t/RC
t = Ln10×R×C
t = 7.7µs
Dr. Hazem Falah Sakeek