what happens when a wire that carries electric current is placed in a magnetic field

When a current carrying wire is placed in a magnetic field, it experiences a mechanical force. This was discovered by Michael Faraday in 1821. The wire will not experience any mechanical force if it is placed parallel to the magnetic field. And the force will be maximum if the current carrying wire is placed in a direction perpendicular to that of the magnetic field. The force exerted on the wire is known as the Lorentz force.
We can use Fleming's left-hand rule to determine the direction of the force experienced by the wire. According to Fleming's left-hand rule, if we stretch the forefinger, middle finger and the thumb of the left hand, and the forefinger represents the magnetic field, middle finger the current, then the thumb will represent the direction of the force.
Interestingly, if the wire is not held in place, then the mechanical force may cause its motion.
Hope this helps.
https://nationalmaglab.org/education/magnet-academy/watch-play/interactive/right-and-left-hand-rules