When designing a low voltage switching device it is essential to know the forces acting on the moving contact member in order to achieve optimal mechanically operation. A major contribution is provided by the magnetic force associated with the current constriction close to the small regions where electrical contact is actually provided (Holm force). Previous results show that this repulsive force depends strongly on the number and positions of contact regions, parameters which may vary from case to case. In order to avoid such a statistical behavior one can use contact plates not having flat surfaces but rather shaped in such a way that the contact regions are well defined and predictable. In this paper we investigate by numerical simulations how the Holm force varies for different shapes of the contact plates, corresponding to different number, positions, and shapes of contact regions. Among other things it is demonstrated how the force depends on the position of one single contact spot, the number of contact spots distributed in a matrix, and the position and length of elongated, "ridgelike", contact areas. Of particular interest is the observation that such ridges can be used to produce a negative, i.e. attractive, Holm force.
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