Recently i had to change out 110 volt outlets in my kitchen and found that even though i shut off the breaker to the outlet i got a big surprise a shock. I found that the outlet has 2 power source into it. Is there any case where some one would wire in 2 power sources into one 110 volt outlet.
Yes you could have two circuits in one duplex receptacle. When this is done the tab is removed that connects the two screws together on the brass side of the receptacle where the hot conductor is connected. Removing the tab will allow the top receptacle to be on a different circuit from the bottom. The neutral tab on the receptacle may have to be removed as well if the neutral is not shared. Split duplex receptacles are common in rooms that use a switched receptacle rather than a light opening.