The induced charge on a grounded arbitrary conductor, excited by a nearby point charge, is shown to be approximated by that on an equivalent conducting sphere near the same point charge. The proof is modified from that for capacitance by Payne and Weinberger [J. Math. Phys.33, 291 (1955)]. A number of examples for different grounded blocks and plate are given. The potential field distributions from the induced charge are also given.