Today, in this short article, we will try to explain in simple terms the basic workings of an electric motor. As a fundamental concept, we must bear in mind that an electric motor is a device that converts electrical energy into mechanical energy. The simplest model is the direct current one, made up of a rectangular metal loop free to rotate, called the rotor, placed inside a uniform magnetic field generated by the two opposite poles (positive and negative) of the stator. The magnetic forces exerted on the loop act on one side and on the opposite side, producing equal forces in opposite directions, and this causes the loop to rotate until it reaches a horizontal position. To keep the loop rotating, the direction of the current must be reversed, so as to reverse the direction of the forces.
This is where the commutator and the brush come into play: the former consists of two half-rings that turn with the loop and are attached to its ends, while the brushes are two sliding contacts, one positive and one negative, which supply energy and are connected to the half-rings. Each time the loop turns, the half-rings change brush, switching the contact at every half turn (first negative and then positive, and vice versa) and therefore the direction of the current, so that there will always be a force pushing the loop to continue its rotation. In this way, electrical energy sets the loop in motion.
