When dealing with voltages and amperage, which one can destroy your equipment when not properly matched to the proper device? Am I correct in thinking that attempting to charge a device with an adapter of the correct voltage but too low an amperage won't damage the device but will just take longer to charge?
Note: Main OK point from below is that a power supply with the correct voltage rating and a higher than specified current rating will be OK to use in the vast majority of cases. The situations where this does not work are so rare as to be worth risking unless major safety or $ value concerns exist. Even then you can probably check with over current supply at correct voltage and see if problems occur. If the equipment is worth over 2 weeks income get the correct supply :-).
Power = Volts x Amps = V x I
Too high Voltage will do damage.
Too low voltage may do damage.
Slightly too low may work AOK or at reduced current.
Too low may damage equipment but not usually.
Correct voltage rating and too high current rating is USUALLY OK - equipment will take what it needs.
Correct voltage rating and too low current rating may cause damage.
Using an adapter with under-rated current could result in a couple of different outcomes, depending on the particular adapter. (Assuming that since you said 'device' and not just 'battery', that we're talking about devices that have managed batteries in them, which is pretty common now)
A very cheap one might overload and burn out. Device will take very much longer to charge.
A better one, with protection will reduce its output voltage to keep the current constant, in which case, due to the reduced voltage, your device won't charge much faster than in the first case.
You actually want an adapter that has as much, or more, current capacity than the device you're trying to power. The current marked on the adapter isn't the current you necessarily get, you see, it's the upper limit of what the adapter wants to provide. The amount of current you actually get depends on the device, and if it demands too much, your adapter will suffer.