A thick metal slab carries a current I as shown. A uniform magnetic field B points perpendicular to the slab (and into the page). If point P on the slab is at a higher potential than point Q , what can we say about the charge carriers that produce the current in the slab?

Question

A thick metal slab carries a current I  as shown. A uniform magnetic field  B points perpendicular to the slab (and into the page). If point P  on the slab is at a higher potential than point Q , what can we say about the charge carriers that produce the current in the slab?
a.They are positive.  
b.They are negative. 
c.They could be either positive or negative, but we can't tell without more information.  
d.The situation is impossible: point   could never be at a higher potential than point  , no matter what the sign of the charge carrier
( P is upper side and Q is lower side)
I think upside( at p) electrons are more because of higher potential, so they are negative. But I am not sure. pls help me

Damon · Answer

Usually one would assume a metal slab is a conductor and there is no potential difference between top and bottom. I would be inclined to say d but do not have the picture entirely.

Anonymous · Answer

has anyone checked if A was the right answer?