posted by Raul .
A current I = 16 A is directed along the positive x-axis and perpendicular to a magnetic field. A magnetic force per unit length of 0.15 N/m acts on the conductor in the negative y-direction. Calculate the magnitude and direction of the magnetic field in the region through which the current passes.
When the current I and mgnetic field B are perpendicular,
F = B I L
In your case, force per unit length F/L = 0.15 N/m; therefore
B = (0.15 N/m)/16 A = 9.4*10^-3 Tesla
The direction of the field is the z direction. As to whether it is up or down, use the right-hand rule to get the direction of I x B, and make sure it is in the -y dorection