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Two charges q₁ and q₂ are placed 30 cm apart, as shown in the figure. A third charge q₃ is moved along the arc of a circle of radius 40 cm from C to D. The change in the potential energy of the system is q₃ / 4πϵ₀ - k, where k is
- 8q₁
- 8q₂
- 6q₁
- 6q₂
Correct answer: 6q₁
Solution
The change in potential energy depends on the work done in moving the charge q₃ along the arc. Since the distance from q₁ to q₃ remains constant (40 cm), the potential energy change is determined by the interaction with q₁. The factor of 6 arises from the geometry of the problem.
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