just like in the title, will this power adapter work with arduino? link
(The EU 3A variant)
it will work BUT when powering Arduinos you are better with a slightly lower voltage 7.5 to 10 Volts.
There seemed to be a period where 12 volts was causing some issues with components on the real Arduinos.
Clones seemed unaffected.
The higher the voltage the more work the regulator has to do to reduce the voltage to around 5 volts.
The reduction in voltage just generates heat in the components.
Also you dont need any more than 1 Amp.
If you are running other items such as motors etc they should have thier OWN power supply with just a shared common ground.
If that is the case then order another PSU. AT that price it is a bargain...