Force on a Current Carrying wire in a Magnetic Field —
When a straight conductor of length $l$ carrying current $I$ is placed in magnetic field, it experiences a force given by
$F=I(\vec{l} \times \vec{B})=I l B \sin \theta$
Here, $\theta$ is angle between $\vec{l}$ and $\vec{B}$.
Fleming's left hand rule —
The direction of the force $\vec{F}=I(\vec{l} \times \vec{B})$ is given by the Fleming's left hand rule. Close your left hand first and then shoot your index finger in the direction of the magnetic field.
Relax your middle finger in the direction of current. The force on the conductor is shown by the direction of the erect thumb.
