Chapter-2|Electrostatic Potential and Capacitance| NCERT 12th Physics:
Electrostatic Potential Energy of a System of Three Point Charges:
Let we consider a system of three point charges q₁, q₂ and q₃ having position vector r₁, r₂ and r₃ respectively.
If we bring charge q₁ from infinity to point A, no work is required because there is no any electric field there. So