This section will show you how a basic direct current (DC) motor works. In further sections we'll look at other devices that eploy electromagnetic induction.
The first thing you'll need to do is to familiarize yourself with the basic anatomy of an electric motor. See the diagram below for that.
The armature is a piece of metal that can be magnetized – a ferromagnetic metal like iron. Wrapped around it are windings of wire to form an electromagnet. What's special about it are a set of contacts, one connected to each end of the windings, called the commutator. They form a circle, but the contacts (black and gray in the figure below, green and magenta in the other figures that follow) are separated by a small gap. That gap is a little wider than the brushes.
The brushes (so called because in older motors they were often made of metal fibers) contact the poles of the battery through the poles of the commutator. The commutator arrangement ensures that the polarity of the armature is switched ever half turn of the motor.
In the eight steps below you can follow a single cycle of a DC motor in detail. See if you can work through the logic of how the motor works. It'll be worth it.
You can read down the left side of these steps, or down the right side. Each expresses the steps a little differently, so try them both. See which works for you.
Notice that in this position, the armature would experience a clockwise force as the north poles and south poles of the armature and permanent magnet repel each other. So already our motor is turning.
The north pole of the armature is now attracted to the south pole of the permanent magnet, and the south pole of the armature is attracted to the north pole of the permanent magnet; the turning force continues.
The inertia of the armature will now carry it through to the next step, in which the brushes will contact the poles of the electromagnet in the other of the two ways they can.
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