AC vs DC to arduino pins

Total newbie question. Just got my Arduino in the mail and am teaching myself electronics. My first project will be a sort of power meter and so I am wondering if the output from my coil transformer (AC) can be sent to one of the Arduino analog I/O pins, or if I need to change it to DC first?

I can only assume this sort of question has been asked by many newbies be fore me, so if there is a standard place you could send me to to find the answer, that would be great!

Thanks Ray

You can't connect voltages to the Arduino that go outside the power rails of the device, this is a almost universal rule for semiconductors.

It can be AC but only if it is within the 0 to 5V range. Most AC will go negative and damage your Arduino. Therefore best to turn it into DC. Although sound waves are AC and can be connected like this:_ http://interface.khm.de/index.php/labor/experimente/arduino-realtime-audio-processing/