In what case does a magnetic field have no effect on a current-carrying conductor?

The magnetic field will have no effect on the current conductor if the conductor is placed along the lines of force of the magnetic field. This is due to the left hand rule. If you put a conductor with a current between the poles of a magnet perpendicular to the lines of force of the magnetic field, then you can notice the following that by placing your hand so that the lines of force are directed to the palm and the hand is located in the direction of the current flow in the conductor, then the thumb bent 90 degrees , will show the direction of movement of the conductor.