My young son's friend came around to our house the other evening with his
notebook pc. The friend's battery started running low, so my son took the
transformer from my wife's laptop and plugged it into his friends computer.

I was horrified that he hadn't checked the voltage the amperage or the
polarity. He knows more than me about computers, but was he right to not
check these things or does a few volts, the polarity or the likely
difference in amperage between notebook computers not matter much.
grateful for other opinions on this. thanks.