Alternating current generation

sketchfab

We create a persistent magnetic field within which we cause a coil to spin steadily. As a direct result, an alternating current is produced. Why does it alternate? The magnetic field generated by the current inside the coil (purple) always attempts to counteract the original field, so the current must flow in the direction of the green arrows. To accomplish this, it must continually change direction to adapt to the coil's rotations, resulting in the blue current.