NOTE: When there is a
complete circuit, power does go
back and forth between the hot and neutral. Therefore if there is a complete circuit at the computer end of the cord and you measure voltage between ground and the neutral wire you will see 110VAC -just as if you had measured from the hot wire!
And since there is no proof that a house is wired correctly (the hot can be at either side of the receptacle and everything will appear to work correctly), checking an open circuit relative to ground is the only easy way to know for sure which is the hot.
