الفيزياء العامة الجزء الثاني#موقع الفيزياء.كوم

Direct Current Circuits
Example 8.7
In the circuit shown in figure 8.14, (a)
find the current in the 2Ω resistor, (b) the
potential difference between points a and
b.
(Use the current as labeled in the figure
8.14).
a
12v
I 1
I 3
2Ω
I 2
4Ω
b
8v
6Ω
Figure 8.14
Solution
At junction a we get
I 1 = I 2 + I 3 (1)
For the top loop
12 - 2×I 3 - 4×I 1 = 0 (2)
For the bottom loop
8 - 6×I 2 + 2×I 3 = 0 (3)
From equation (2)
I 1 = 3 - 1/2 I 3
From equation (2)
I 2 = 4/3 - 1/3 I 3
Substituting these values in equation (1), we get
I 3 = 0.909A the current in the resistor 2Ω
The potential difference between points a and b
V a - V b = I 3 ×R = 0.909×2=1.82v
V a > V b
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