The direction of Ampere force F is not only perpendicular to the magnetic field, but also perpendicular to the conducting wire, that is, f is perpendicular to the plane where Bi is, but the direction of B and I is not necessarily perpendicular

The direction of Ampere force F is not only perpendicular to the magnetic field, but also perpendicular to the conducting wire, that is, f is perpendicular to the plane where Bi is, but the direction of B and I is not necessarily perpendicular

A line perpendicular to a plane is perpendicular to any line in the plane
Suppose the leg of the stool is f, and the ground is the plane of Bi. You put two wooden sticks as B or I. no matter how you put them, the two wooden sticks are perpendicular to the leg of the stool. You can have a try

If a 2-meter-long conducting wire with 1a is vertically placed in a uniform magnetic field with 0.5T magnetic induction, the ampere force on the conducting wire will be small

F =BIL =2*1*0.5=1