Sent from my stock iPad 2
Another way to look at it; You can fully charge your iPad, unplug it, use it heavily and you will drain it in less than 10 hours. You can take a drained iPad, with the 2.1 Amp charger (the big one) and it takes 10 hours or more to charge if you are not using it at all. You can see that you are able to drain the battery faster than you van fill it back up. It is kind of like a bathtub, you can fill it with the stopper in, you can drain it without running the water and it will empty. You can also turn the water on and pull the plug and the tub will empty even though you are trying to fill it as fast as you can.
One way to see how much you are draining would be to make a note of the % battery left and plug it into your wall charger
Then while still connected to your wall charger use your ipad heavily for an hour. Maybe open the number of apps you often keep open, do a bit of web browsing, check emails and play an intensive game or two
Now disconnect the Ipad from the charger and look at the % battery power on your Ipad.
If the % is higher than it was before you plugged it in and started using the ipad then you are not draining the battery more than the charger is adding.
If the % battery power is lower then you know you are using more battery power than is being input by the charger.
All great answers.
I was always of the opinion that the charger could by-pass the battery and supply power.
Many items I have work that way ( I think ) 😜