Question 1

?How is this cooler powered?

Accepted Answer

The cooler is powered via laptop's USB port.  The USB cable comes attached to the cooler and all you have to do is plug it into the laptop's USB port.  Hope this helps

Question 2

Does it feel comfortable when placed on your lap when using a laptop? Does it fit in an average sized backpack?

Accepted Answer

The only way this would be comfortable, or even usable, on your lap is if a board were placed between it and your lap. Without a board you would be blocking the fan and negating the cooling.  
It should fit in a typical backpack along with a notebook computer.  
I found the biggest advantage to this unit being the ability to adjust the fans to a place where they do the most good (directly under the intake vent on the notebook). Most notebooks don't have the vents in a central area. 
My notebook is a model that is known for over-heating and I had to replace the motherboard as a result. So far this fan seems to be keeping the new motherboard running...

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