We discuss about the antibacterial activities of copper nanoparticles on both Gram negative and Gram positive bacteria in this investigation. First time, we increase its antibacterial activities by using electrical power while on electrolysis synthesis and it is confirmed from its more antibacterial activities (For Escherichia coli bacteria). We investigate the changes of surface area to volume ratio of copper nanoparticles prepared in two different methods and its effects on antibacterial activities. We note that slight change of surface area to volume ratio results in the enhancement of its antibacterial activities.