You also have a box full of power supplies and don't know which one goes with which? It doesn't really matter, basically you can take any, as long as the volts and amps are right: Volt, i.e. the voltage must match the device and power supply unit; if the power pack delivers too much voltage, the device (tends to) break down, if it delivers too little, the device doesn't work. at Ampere However, this is a maximum specification: If the device requires more amps than the power supply unit can supply, it will not work and the power supply unit will break (unless it is fused). If the device requires fewer amps, the power adapter is simply not fully utilized.
The right power supply with the right voltage
A power supply with 5 volts and 1 amps can therefore be used for all devices that require 5 volts and 1 ampere or less (which is not to say that a device here and there is not particularly finicky and cannot, for example, cope with the voltage fluctuations of a non-original power supply). And if you multiply both, you get the power consumption in watts: A typical USB power supply (e.g. from a smartphone) with 5 V and 2 A has a maximum output of 10 watts.
And since such questions keep coming up, here they are again in brief:
- Volt must fit exactly.
- Ampere may be higher for the power supply.
Example: 5 amp, 12 volt power supply can power devices that exactly 12 volts and maximum 5 amps desire.
By the way: There is a handy Watts/Amps/Volts calculator here.
PS: A previous version of the article had different numbers, so some of the comments are no longer applicable - just for clarity.
PPS: Since the article has been very popular for 9 years now and has raised all kinds of questions, there is now a whole website based on it with much more information about volts, amps, watts and power supplies - have a look VoltAmpereWatt.de.
Addendum: Here are a few links to universal power supplies that might be useful:
First the variant for normal home use with 3 to 12 volts at 2 amps:
Something similar is also available for laptops:
And for the daring, of course, there's that, too really universal universal power supply – including the option to scrap everything that comes near it:
So serious: Be careful with universal power supplies! It cost me a camera many years ago because I had set 9 instead of 6 volts ...