Bubbles play an important role in the transport phenomena existing in an electrolysis cell. They increase the total ohmic resistance of the electrolyte but their contribution is still not well quantified. During their movement under the anode, the bubbles are separated from the solid by the so-called wetting film, that is by a thin liquid layer. In order to develop a mathematical model to compute the increment of the electrical resistance of the electrolyte due to the presence of several bubbles under the anode, the effects of the bubble shape and the thickness of the wetting film for a single bubble must be quantified a priori. In this first paper, these effects are computed using the finite element method (FEM). The results have shown that the influence of the bubble shape and that of the wetting film is small, about 5% and 2%, respectively.