Question

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

Huh? cross product is zero

Answer 2

Huh! Cross product is zero.

Answer 3

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

Note here sin theta = 0 so no force
In your other problems theta is not zero.