الفيزياء العامة الجزء الثاني#موقع الفيزياء.كوم

Electric Potential Difference
Example 5.14
In the rectangle shown in figure 5.17, q 1 = -5x10 -6 C and q 2 = 2x10 -6 C
calculate the work required to move a charge q 3 = 3x10 -6 C from B to A
along the diagonal of the rectangle.
q 1
q 3
15cm
A
5cm
B
Figure 5.17
q 2
Solution
from the equation
V B -V A = W AB / q o
V A = V 1 + V 2 & V B = V 1 + V 2
VA
=
4
q
πε ο
− 6
−
⎡ − 5×
10 2 × 10
⎢
+
⎣ 0.15 0.05
6
⎤
⎥
⎦
= 6 × 10 4 V
VB
=
4
q
πε ο
− 6
−
⎡ − 5×
10 2 × 10
⎢
+
⎣ 0.05 0.15
6
⎤
⎥
⎦
= -7.8 × 10 4 V
W BA = (V A - V B ) q 3
=(6 × 10 4 + 7.8 × 10 4 ) 3 × 10 -6 = 0.414 Joule
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