If you try to connect it to a newer Apple device (assuming you can find a FireWire cable), it won’t work, but nothing will blow up. On the surface, it looks like a USB charger, but it actually has a FireWire port instead. The one to watch out for is the square white Apple charger supplied with original and early model iPods. In between -using one of the older 10W iPad chargers on an iPad Air- it will take a bit longer for the iPad’s battery to top up. If you step down too far -using the little 5W adapter to recharge an iPad Air- it simply won’t work.
If you use a USB charger with a higher wattage than the the one your device originally shipped with -for example, using one of the 12W iPad chargers with an iPhone- you may find the battery charges slightly faster, but Apple says it’s safe to do so. So long as you stick with Apple rechargers, there’s not much you can do to hurt yourself, or your Apple gear. Apple chargers, common US types (Credit: Apple).
