From the work of the electric contacts technology’s most respectable researcher, Ragnar Holm, the main physical questions about the functioning of the electric contacts, like the physical background of the constriction resistance and the contact resistance and the dependence of contact load and the temperature in the contacts, have been introduced in my thesis. One of the most important points of the technology is the type of the contact materials consequently the developing of tarnish films of these metals have been demonstrated in this thesis. Demonstration of the mostly used contact metals in the practice is also a part of the thesis. In the utilization of this knowledge of materials various types of electric contacts have been measured. With the great use of four-wire measurements some type of contact characteristics, like R-I (contact resistance – current intensity) and P-R (contact load – contact resistance), have been made. In addition to the investigation of surface roughness and load dependence, the creeping of contact resistance on constant current intensity has been examined. The uncoated copper contacts and their tarnish film’s effect on the contact are a specific part of the thesis. In virtue of the results it is clear, that the modern coating technologies are very important in most cases. The particular results of each sample can be found in the attachment at the end of the thesis.