The iPad will charge from anything that provides power over a USB connection per the specs. However, the iPad likes to negotiate an out-of-spec power draw, which it can from certain Macs, or the charger it comes with. With those devices it can both charge and be run at the same time.
With normal USB power it can either charge, or run, but not both. So if you run it you will see a notification that it is not charging. When you deactivate the iPad it actually will charge (but you can't see the notification that it is doing so).
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No. The iPad's charger is 10 watts. You need to use its specific charger or plug it into a computer.
I've been using my iPhone 4 charger on the iPad for some time. Works fine.
With normal USB power it can either charge, or run, but not both. So if you run it you will see a notification that it is not charging. When you deactivate the iPad it actually will charge (but you can't see the notification that it is doing so).
No. The iPad's charger is 10 watts. You need to use its specific charger or plug it into a computer.
Simply not true.
To the OP: ... charge away, your MIL will be just fine with an iPhone charger, it'll just take longer.