Voltage drop across the 100 feet ethernet cable

Today we wanted to make sure we can send 48V through our 100 feet ethernet cable without losing more than 12V while pulling about 3A.
So I devised the following setup to figure out the voltage drop across the cable.
















At first I used a 150 W lamp in series and the voltage drop across the cable was about 2V from 1A. Eventually I used two rheostats for a lower total resistance and the voltage drop was 7.2V while pulling 3A. This proves that we can send the power for the cameras and otterbox through the cable without harming it.