Lesson Summary Now that the students have learned what is inside a motor, they use the armature of the motor they disassembled in Lesson 14 to experiment with variables that have an effect on the motor’s operation.  They use what they have learned to reassemble the motor and test to ensure that it is working properly. Teacher Background The purpose of taking apart the motor in Lesson 14 was to see what is inside it.  In this lesson, students discover how all those parts work together. At this point, students know that a motor needs electricity, magnetism, and a special switch in order to function. Now, they are provided with an opportunity to experiment with these elements. In this lesson, the brushes of the motor will be two wires that make direct contact with the commutator.  The students will use the armature that they removed from the motor.  The magnets are the same as those they have been using since Lesson 2.  All of these items will be assembled on a “test stand”-where the parts can be seen and manipulated easily.  This setup is shown in Figure 15-1. There are several variables that students can change that have an effect on the operation of the motor: the location of the magnets (above, below, or to the side of the armature) the proximity of the magnets to the armature the poles of the magnets facing the armature (if like poles face the armature on opposite sides, the motor will not turn; also, the direction of spin can be controlled by reversing the poles) the number of batteries providing electricity to the electromagnets on the armature the direction in which the electric current flows (this can be changed by flipping the battery over in its holder) the presence of absence of electric current (achieved by turning a switch on or off or by disconnecting the circuit) By exploring ways to control the motor, the students develop for themselves a concept of how a motor works.  They then use what they have learned to put the motor back together and to test to see that it is working. Set-up/Management Tip 1.  Prepare the materials for distribution. Note: If this is the first time that the materials have been used, you may have to construct double strands of hook-up wire from the 2 pieces you have for every student.  Students could help with this task.  Strip both ends of two pieces of #20 wire (each 30 cm. 12 inches, long) and fasten the wires together with electrical tape.  The tape should hold the wires together where the insulation ends and the bare wire begin. 2.  You will need the electric motor (taken apart) from the last lesson. Materials can be handed out in numbered baggies. If this is the first time this unit has been used, then you will need to have made the double-strand hook-up wire by taping together two pieces of #20 wire. 3.  Again, depending on the amount of materials available, you may want to have students work together in groups of two or four for the lesson. Again, neatness in construction is very important. 4.  The placement of the magnets is also important. You may want to experiment yourself to see outcomes of different placements. Literacy Support Have students draw a picture of their set-up in their science notebooks.  See the Student Activity Book for Lesson 15. Scientific Vocabulary The following words are key vocabulary words that will be introduced in this lesson and reinforced throughout the unit: No new vocabulary introduced this lesson.