Lesson Summary In the last two lessons, students built two different kinds of motors; now they will investigate small, commercially produced motors.  Each student makes the motor operate and then takes it apart.  This lesson is the link that joins the magnet investigations begun in Lesson 1 with the electromagnet and motor lessons. Teacher Background People, particularly young people, seem to have an innate curiosity about how things work.  From a baby’s rattle to a computer, children want to look insides and see what’s going on.  An electric motor is no exception, but, until the advent of inexpensive miniature motors, it was impractical for large numbers of students to dismantle one. For this reason, few people understand how a motor works or what is inside it. The motor that students experiment with in this lesson operates on current from a battery.  It uses two permanent magnets (attached to the inside of the case) and three electromagnets (wound around the rotor, which is also called the armature). The automatic switching that was discussed in Lessons 12 and 13 is performed by the motor’s brushes and commutator.  See Figures 14-1 and 14-2 from the Teacher’s Guide for two different views of a motor. As the magnets and electromagnets attract and repel to rotate the armature, the brushes make contact with different segments of the commutator.  These segments are connected to the three electromagnets.  As the motor rotates, the brushes touching different commutator segments cause the three electromagnets to be turned on and off continuously.  Figure 14-3 from the Teacher’s Guide shows how the motor rotates. The direction of the electric current through the wire coils also switches each time that the brushes move to a new pair of commutator segments.  Changing the direction of the current changes the polarity, or “where the poles are”.  The north and south magnetic poles change places.  This allows the electromagnets and the permanent magnets to attract and repel, depending on where the electromagnet is in its travel around the inside of the motor.  Automatic commutator switching is an extremely clever technique that took years to develop.  Do not expect the students to grasp all of his intricacies right away. Set-up/Management Tips Prepare the materials for distribution.  Make sure that the ends of the wire motor leads are stripped and the exposed strands twisted.  Student helpers could be recruited for this task. You may wish to dismantle partially the device you will be demonstrating when you begin the lesson. You may want to purchase a small electric toy to show as a demonstration for this lesson. Again, hand out materials using the numbered baggies.Each student should have his or her own motor (if you have enough materials). Make sure students understand that they do not take the motors apart until they have done Steps 1-4 in the Student Books. You may need to help students understand that reversing the wire hookup or turning the battery around will change the direction of the motor. You should also go over vocabulary so that students can talk about the armature and the commutator. Again, make sure you have taken apart one of the motors ahead of time so you can help students. Putting motors back together without breaking parts is very tricky. If you have someone to help you put motors back together, it might be better not to have students do this. If you have enough supplies, wait until Lesson 15 to put them back together. Literacy Support You could have students draw and label pictures of the inside of a motor in their science notebooks.  See the Student Activity Book for Lesson 14. Scientific Vocabulary The following words are key vocabulary words that will be introduced in this lesson and reinforced throughout the unit: *armature *commutator *brush *permanent magnet