Answer:
Magnetic force
Step-by-step explanation:
An electric motor converts electric energy to mechanical energy. When a current carrying coil is placed in changing magnetic flux, a magnetic force - torque is exerted on the coil and it starts rotating.
In the given case, an alternating current flows in the electromagnet so magnetic field continuously changes direction. Axle placed between these electromagnets experiences magnetic force. The torque produces causes the axle to spin.