Electrical contacts are used in general electrical applications such as circuit breakers, switches, relays, connectors, etc. Repeated separations of the parts (anode and cathode) of these contacts under input power can damage their contact materials. The objective of this work is to study the influence of the input electric power (100 W and 256W) and the contact sizes (hemispherical contacts with diameters D=5mm and D=8mm) on the variation of the arc energy and the damage of the contact surfaces by oxidization or by erosion. These parameters are decisive for selecting the best arc-resistant contact sample. Experimental results, SEM, and EDX analysis show that high input power leads to more degradation of contact surfaces. Also, the smaller and the larger contact diameters generate similar arcing energies with similar erosion sizes and oxidation rates, but contact with a small diameter has a higher lifetime (1215 operations) and oxidizes less quickly than the one with a large diameter that has a lower lifetime (374 operations). Experimental and numerical analyses demonstrate that arc mobility is one of several factors influencing the change in contact lifetime.