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COMEDK202510 May 2025Evening ShiftPhysicsElectrostaticsActual

Three point charges -1 C,+1 C,+1 C are placed at points A , B , C respectively of a triangle ABC . What is the total potential energy of the system? [given AB = AC =6 ~cm and BC =3 ~cm ]

Options

  1. A0 J (Zero joule)
  2. B4.5 10¹³ J
  3. C3 10¹³ J
  4. D6 10¹³ J

Correct answer

A. 0 J (Zero joule)

Step-by-step solution

The potential energy U of a system of point charges is given by the sum of the potential energies of all pairs of charges: U = k ( q_A q_B r_ AB + q_B q_C r_ BC + q_A q_C r_ AC ) , where k = 9 10^9 N m ^2 C ⁻² . Given charges are q_A = -1 C , q_B = +1 C , q_C = +1 C . Given distances are r_ AB = 6 cm = 0.06 m , r_ AC = 6 cm = 0.06 m , and r_ BC = 3 cm = 0.03 m . Substituting the values into the formula: U = 9 10^9 ( (-1)(1) 0.06 + (1)(1) 0.03 + (-1)(1) 0.06 ) U = 9 10^9 ( - 1 0.06 + 1 0.03 - 1 0.06 ) U = 9 10^9 ( -

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