Actually USB is a great example. USB C can charge at 5v, 10v, 20v, etc. When you plug in a device to the charger a hand shake happens between the charger and d

Actually USB is a great example. USB C can charge at 5v, 10v, 20v, etc. When you plug in a device to the charger a hand shake happens between the charger and device and they choose the voltage and amperage that makes sense. A macbook pro can take 100W over USBC but obviously your headphones or phone aren't going to.