Almost every material that conducts electrical current has some resistance that limits the current. This resistance depends on the length of the conductor. The resistance generates a voltage drop over the conductor/cable that increases when the current and/or the length increases. The item at the end of the conductor receives less power than what the power supply delivers. That item can become faulty or can get damaged when this voltage drop becomes too large. This power drop can sometimes be felt when the cable is getting warmer.