We have a square loop (I believe it's called) in a uniform magnetic field between the 2 poles of a permanent magnetic field (green is N, red is S). P is connected to the positive pole of a voltage source and Q is connected to the negative pole (so there is a current):
- Show the direction of the Lorentz force
The magnetic field lines point towards S from N. There is no Lorentz force at b, because the angle between the current and the field lines is $180^o$. Using the left hand rule we find that at h the lorentz force goes 'into' the paper and at the right side of h the Lorentz force goes out of the paper.
My book says that the magnetic field lines face from N to S, which causes opposite answers. Why is this? I'm thinking it has to do something with $P$ and $Q$, but I'm not quite sure..