When is the magnitude of force maximum in a current-carrying conductor?

The magnitude of force maximum in a current-carrying conductor when the direction of the current is at 90^o to the direction of the magnetic field. 

Experiments to demonstrate the force due to a magnetic field acting on a current-carrying conductor have proved that the displacement of the rod is the largest (or we can say that the magnitude of the force is the highest) when the direction of current is at right angles to the direction of the magnetic field.