Electrospinning is a simple method used in the preparation of polymer fibers, the diameter of the electrospun fibers, varying in large from micrometer to nanometer, mainly depends upon the electrical field applied. The non-linear relation between the current of charged jet and the applied voltage is an intriguing and enduring problem. An allometric scaling relation between the current and voltage is obtained. He Chengtian's inequality, which has millennia history, is applied. (C) 2004 Elsevier Ltd. All rights reserved.