# How do Lorentz forces occur in brushless DC motors if the flux lines are guided past the coil

In a brushless DC motor, the permanent magnet of the rotor creates a magnetic flux which moves through one stator pole shoe, through the back iron and returns to the opposite pole. The magnetic field lines pass through two poleshoes/coil cores. If the flux is contained to this iron path how does it generate force? As the Lorentz force is given by $I \times B$ and $B$ is zero outside the iron (where the current is), shouldn't $F$ be zero as well?