Powered USB Hub with Arduino

I was wondering if i could use a powered USB hub with an Arduino while also having the hub plugged into the computer? My hope is that this will deal with the over draw that occurs when only connected to the computer.

Idea:
(5V @ 700 mA A/C adaptor) + (5V @~500mA USB)=5V @1.2 A and communication

I want to do this to power the arduino AND communicate with it at the same time, so I can see the results of my code immediately.

Concern:
Back voltage. I am terrified that the $6.00 adaptor i want to buy will put back voltage into my computer and break something with this set up.

Any comments or ideas would be appreciated.

I use an external powered USB HUB with Arduinos.

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Back voltage. I am terrified that the $6.00 adaptor i want to buy will put back voltage into my computer and break something with this set up.

I don't see how. The hub is designed to be connected to your computer so it is unlikely there is even a 5V input to the hub from the PC since the 5V out would come from the hub power supply . If there is a 5V input pin on the hub usb cable that plugs into the PC it only makes sense that there is no connection from the PC 5V to the 5V ouput available on the hub USB connectors. Think about it for a minute. How could the PC 5V be connected to the hub output 5V ? The only way I could suggest for to verify this is find a way to do a continuity test from the USB connector that plugs into the PC to one of the usb connectors on the hub with nothing connected to any power.