A vertical straight wire 35.0 cmcm in length carries a current. You do not know either the magnitude of the current or whether t
he current is moving upward or downward. If there is a uniform horizontal magnetic field of 0.0300 TT that points due north, the wire experiences a horizontal magnetic force to the west of 0.0180 NN. Find the magnitude of the current.
I would say it’s “B” for the reason that the student did not experiment with a short ramp and large ball as well as a large ramp and a short ball. They have to do those experiments as well before drawing their conclusion.
Since compasses work by pointing along magnetic field lines, this means that there must be a magnetic field near the wire through which the current is flowing.