The flow and heat transfer of an incompressible electrically conducting fluid over a rotating infinite disk are studied in the present paper. The disk finds itself subjected to a uniform normal magnetic field. The particular interest lies in searching for the effects of an imposed radial electric field on the behavior of the physical flow. The gradient of an electric potential generated on the disk penetrates through the fluid and greatly influences the boundary layer formation. The presented model representing the fluid motion is a general case since it reduces to the traditional Karman's viscous pump when the electric potential is ignored. The governing Navier-Stokes and Maxwell equations of the constructed model together with the energy equation are converted into self-similar forms using suitable similarity transformations. The flow and thermal boundary layers are shown to be much affected by the presence of a uniform radial electric parameter. Some parameters of fundamental physical significance such as the surface shear stresses in the radial and tangential directions and the heat transfer rate are numerically evaluated. The effects of electric conductivity of the disk on the flow and forced convection heat transfer are further discussed. (C) 2011 Elsevier Ltd. All rights reserved.