Английский язык: Аннотирование и реферирование текста

257 More Parts The axle holds the armature and the commutator. The armature is a set of electromagnets, in this case three. The armature in this motor is a set of thin metal plates stacked together, with thin copper wire coiled around each of the three poles of the armature. The two ends of each wire (one wire for each pole) are soldered onto a terminal, and then each of the three terminals is wired to one plate of the commutator. The final piece of any DC electric motor is the field magnet. The field mag- net in this motor is formed by the can itself plus two curved permanent magnets: One end of each magnet rests against a slot cut into the can, and then the retaining clip presses against the other ends of both magnets. Electromagnets and Motors To understand how an electric motor works, the key is to under- stand how the electromagnet works. An electromagnet is the basis of an electric motor. You can understand how things work in the motor by imagining the following scenario. Say that you created a simple elec- tromagnet by wrapping 100 loops of wire around a nail and connecting it to a battery. The nail would become a magnet and have a north and south pole while the battery is connected. Now say that you take your nail electromagnet, run an axle through the middle of it and suspend it in the middle of a horseshoe magnet as shown in the figure below. If you were to attach a battery to the electromagnet so that the north end of the nail appeared as shown, the basic law of magnetism tells you what would happen: The north end of the electromagnet would be repelled from the north end of the horse- shoe magnet and attracted to the south end of the horseshoe magnet. The south end of the electromagnet would be repelled in a similar way. The nail would move about half a turn and then stop in the position shown. You can see that this half-turn of motion is simply due to the way magnets naturally attract and repel one another. The key to an electric