# What is the principle of a commutator

## Understand physics 4, textbook

45 Electricity determines our lives  Learning objective check 10, page 88 3. How does a direct current electric motor work? In the DC motor model, the power supply is made of graphite pins that press on the commutator. The commutator consists of two metal contact strips that are isolated from each other. In this way, it can briefly interrupt the flow of electricity while it is turning. The immovable magnetic field (field magnet) consists of permanent magnets. The rotating magnetic field (armature) consists of coils with an iron core. In order to achieve constant rotation, the armature is first set in motion and then the power supply is increased. If you swap the plus pole with the minus pole of the power supply unit, the direction of rotation of the motor changes due to the reversed polarity of the armature's magnetic field. The rotating part of an electric motor, which consists of an armature and a commutator, is called the rotor, the stationary part (field magnet) is called the stator. M If the circuit is closed (switched on), the armature rotates due to the mutual attraction of the field magnet and armature. If, for example, the north pole of the armature reaches the south pole of the field magnet, the commutator reverses the direction of the current and thus also the pole of the armature. The anchor turns a little further due to the momentum. So the poles of the same name of the armature and the field magnet come close to each other and repel each other. This leads to further movement until attraction occurs again. 4. How is an AC electric motor constructed? In technical electric motors, the armature is made up of many pairs of coils and armature-shaped steel sheets (iron core). They are arranged in a star shape and connected to the metal parts of the commutator. So-called universal motors, which can be operated with direct current and alternating current, are used for many household electrical appliances and tools. M In an electric motor that is operated with alternating current, the field magnet is also an electromagnet. With alternating current, the poles of the field magnet and armature always change at the same time. This results in a continuation of the rotary movement of the armature. Repulsion Attraction Repulsion Attraction Field magnet Field magnet Brush Brush Rotation by momentum (inertia) 45.1 Representation of the rotation of an armature 45.2 An open AC electric motor 45.3 An electric motor operates the hydraulics. 45.4 Particularly precise running motor of a CD drive 45.5 The electric motor of an electric bicycle For testing purposes only - property of the publisher öbv