A wire that is 46 cm long is parallel to a 0.54 T uniform magnetic field. The current through the wire is 4.5 A. What force acts on the wire?

Answer 1

remember 46 cm = .46 meters

then
http://hyperphysics.phy-astr.gsu.edu/%E2%80%8Chbase/magnetic/forwir2.html

Answer 2

Now of course if the field is PARALLEL to the wire, sin of angle is 0 and the force is zero