A watermill is familiar, and Sansa brightens at the mention of it. "I've seen a watermill before, though I can't say I understand how it works. Some of them, commonfolk use them for separating grain from the husk, or bolting lengths of cloth more quickly."

Yes. This, she understands. "Is that what a motor is? A mill of some sort? But then, how is it different?"

Can it be used for other purposes, these motors?

Can she take that knowledge with her home, and use it against the enemies of her house? She would have influence. She could convince someone to build it for a Stark.