Question about alternator/Battery

I was driving home today when my car died in the middle of the road. I was able to get it off to the side and I realized that I hadn't put my battery cables back into the terminal tight enough when after I was done installing the new starter. Well I fixed that problem and got home without a hitch, but I have a question now, that may just be due to the fact that my belief was incorrect.

It was my understanding that once the car was starter, the alternator took over all power duties, and the battery wasn't needed for any power. This belief would lead me to believe that if my battery had become disconnected while I was driving, my car should have continued on down the road. Am I just incorrect in this?
Author: admin