For 10(b) with the motor side length, I said the rate increases. Here's my reasoning:
* F=BIL, and L halves, so the force on the side 'AB' halves.
* However, this means the mass halves too assuming the mass of the wire per unit length is constant, so acceleration on that part of the wire is constant.
* Now I remembered v=ωr. I assumed the same applied to acceleration (turns out it does: a=αr where α is angular acceleration). If all of the side lengths are halved, then AB is half the distance from the axis of rotation, so the angular acceleration on the motor α=a/r is doubled.
* Hence the rate of rotation doubles too.
Not sure if this logic works, but it was only two marks, so I probably hit at least one of the marks.