Practice question

**System of charges** potential energy is sum over pairs U = Σ k q_i q_j/r_ij, work required to assemble charges from infinity. For 28 μC and -14 μC, 0.28 m apart, U=9×10⁹×28×(-14)×10⁻¹²/0.28= -12.6 J, negative indicates bound system. The charged conductor induces charges on the uncharged conductor: opposite charges on the near side and like charges on the far side. The distance between the opposite charges is smaller than between like charges, so the attractive force (proportional to 1/r² ) between opposite charges dominates over the repulsive force between like charges. This imbalance results in a net attractive force, even though the uncharged conductor has