An approximate expression for Henry's function, describing the electrophoretic mobility of a spherical colloidal particle in the limit of low surface potentials, is developed through a physical analogy to a colloidal particle with a linearly slipping surface (i.e. satisfies the Navier slip condition). The resulting expression reproduces Henry's function with a relative error of no more than 0.1%. This approach is generalized for the electrophoretic mobility of a particle regardless of surface potential though necessary data for rigorous testing is lacking. (C) 2012 Elsevier Inc. All rights reserved.