Abstract
Theonset of Marangoni convection in a horizontal liquid layer, the top surface of which is free and the bottom is a rigid wall, is studied theoretically by the Galerkin method. The electric Rayleigh number Ea and the Biot number at the free surface Bi are taken as variables and the effects of Ea, Bi and the boundary condition for ac electric field at the free surface on both the critical Marangoni number Mac and the critical wave number kc are made clear. It is found that the critical wave number increases rapidly when the electric Rayleigh number exceeds 103 and that the system is stable as long as the following relation is satisfied .
