- Sep 10, 2007
Circuitry in the phone doesn't really have anything to do with it. All USB ports output at 5V, which is one reason you need a charger (AC adapter) in the first place. The circuits in an American home are 120V. If the charger doesn't take that down to 5V for the phone, it's gonna get fried.It makes literally no difference. They are just USB cables... the iPhone uses voltage control circuitry which means if you plug in an iPhone using an ipad charger it will limit the charge it receives / draw less.
If you plug your iPad into an iPhone charger then it will charge, but again, slower.
As for the current involved, all electronic devices only draw the current they need, regardless of protective circuitry. That's why you can use a 50W lightbulb in your home without it overloading (the circuits in your home can deliverin the range of 2,000W).