I have a first generation iPad Air (with up-to-date iOS 8.1)
When I connect it to my 2013 iMac (with up-to-date OS X Yosemite 10.10) - it doesn't work.
Specifically - iTunes automatically launches, but then quickly shows a dialog window that says, "iTunes could not connect to the iPhone. This device is no longer connected."
(That's not a typo - it really says 'iPhone', not 'iPad')
Here's a screenshot:
Meanwhile - on my iPad - in the upper right-hand corner (where the battery life is displayed) - you can see the "plugged in" icon (lightening bolt) rapidly blinking on and off.
In other words - it seems like, when it's plugged in - it's rapidly connecting and disconnecting (several times per second).
If I click "OK" on that dialog window on iTunes - it instantly pops back up, and continues to do so as long as I keep the iPad plugged in.
So - bottom line - I cannot connect my iPad to my iMac.
I'm virtually certain that I was able to connect my iPad before I upgraded to Yosemite on my iMac, and iOS 8 on my iPad.
Thanks in advance for any help!