Two point charges of 1 nC and 2 nC are placed at two corners of an equilateral triangle with side 3 cm. The work done in bringing a 3 nC charge from infinity to the third corner equals the charge times the potential at that point.
Both source charges are at distance 0.03 m from the third corner.
The potential due to the 1 nC charge is V1=0.039×109×1×10−9=300 V
and due to the 2 nC charge is V2=0.039×109×2×10−9=600 V.
Total potential: Vtotal=300+600=900 V
Work done: W=3×10−9×900=2.7×10−6 J = 2.7 μJ