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iv act ity 39 A Simple Motor BROWARD COUNTY ELEMENTARY SCIENCE BENCHMARK PLAN Grade 4—Quarter 4 Activity 39 SC.C.2.2.1 The student recognizes that forces of gravity, magnetism, and electricity operate simple machines. SC.H.1.2.2 The student knows that a successful method to explore the natural world is to observe and record, and then analyze and communicate the results. SC.H.1.2.3 The student knows that to work collaboratively, all team members should be free to reach, explain, and justify their own individual conclusions. SC.H.1.2.4 The student knows that to compare and contrast observations and results is an essential skill in science. SC.H.1.2.5 The student knows that a model of something is different from the real thing, but can be used to learn something about the real thing. © Delta Education. Photocopying and distribution prohibited. ACTIVITY ASSESSMENT OPPORTUNITIES The following suggestions are intended to help identify major concepts covered in the activity that may need extra reinforcement. The goal is to provide opportunities to assess student progress without creating the need for a separate, formal assessment session (or activity) for each of the 40 hands-on activities at this grade level. 1. Remind students that they were again acting as engineers in this activity. Ask, What do engineers do? (They solve problems by designing and building devices.) Remind students that they were given a chance to try out new engineering ideas in Step 8. Tell them to make a list with three columns labeled, “What we tried,” “What we expected,” and “What we noticed.” For each engineering idea or change they made, have students complete a row in their chart. (Answers will vary based on the materials available, time allotted, and inventiveness of the students.) 2. Use the Activity Sheet(s) to assess student understanding of the major concepts in the activity. In addition to the above assessment suggestions, the questions in bold and tasks that students perform throughout the activity provide opportunities to identify areas that may require additional review before proceeding further with the activity. broward county hands-on science Quarter 4 423 424 © Delta Education. Photocopying and distribution prohibited. activity 39 A Simple Motor iv act ity 39 A Simple Motor 4 1 pc OBJECTIVES Students apply their knowledge of electric current and electromagnetism to construct a simple motor. For the class 8 16 16 1 1 roll 1 roll 1 roll 16 pcs 1 pair The students construct a simple motor describe the relationship between electric current and magnetism in a simple motor trace the path of electric current in a simple motor SCHEDULE rubber grommet spacers wire, plastic-insulated, 25-cm batteries, D-cell electrical clips magnets, rubberized ruler, metric tape, masking wire, enamel-coated wire, plastic-insulated wire, plastic-insulated, 15-cm wire cutters *provided by the teacher About 1 hour VOCABULARY armature mechanical energy motor permanent magnet PREPARATION 1 Make a copy of Activity Sheet 39 for each student. 2 From the roll of plastic-insulated wire, cut two 10-cm (4-in.) pieces for each team. Use the wire cutters to strip the insulation off the entire length of each wire. Also cut one additional 25-cm (10-in.) piece of wire for each team and strip just the ends of these pieces. From the roll of enamelcoated wire, cut one piece 30 cm (about 1 ft) in length for each team. 3 Each team of four will need a plastic base, one battery, two electrical clips, one piece of emery cloth, four rubber spacers, two Fahnestock clips, one rubberized magnet, four paper fasteners, two bare 10-cm wires, one 30-cm piece of enamel-coated wire, a piece of masking tape, and two 25-cm pieces of plastic-insulated wire. 4 Have extra batteries, electrical clips, rubberized magnets, and 15-cm (6-in.) © Delta Education. Photocopying and distribution prohibited. MATERIALS For each student 1 Activity Sheet 39 1 pair safety goggles* For each team of four 1 1 2 1 2 1 4 battery, D-cell Delta CircuitworksTM base electrical clips emery cloth Fahnestock clips magnet, rubberized paper fasteners broward county hands-on science Quarter 4 425 BACKGROUND INFORMATION A motor is a device that transforms any kind of energy into mechanical energy. A motor in its simplest form is merely a single coil of wire (an armature) that, when connected to an electrical energy source, creates an electromagnetic field. When the electromagnetic field of the coil interacts with the magnetic field of a permanent magnet, the attraction and repulsion between the two fields causes the coil of wire to rotate. In this activity, students will observe what happens when the magnetic fields of an electromagnet and a permanent magnet interact. lengths of wire available for those students who wish to vary their experiments. Activity Sheet 39 A Simple Motor 1. Use the paper fasteners and rubber spacers to hold the ends of the wire supports and the two Fahnestock clips to the base. The wires should be positioned so that they form inverted “U”s. Position the armature into the looped supports. Tape a rubberized magnet flat under the coil. 2. Insert the battery and electrical clips into the base. Use the 25-cm pieces of plastic-insulated wire to connect the battery to the Fahnestock clips on the armature supports. The armature may need a slight tap to start it moving. 3. Experiment by adding more rubberized magnets and batteries to the setup. What did you observe when you increased the number of rubberized magnets? The armature spun faster. What did you observe when you increased the number of batteries? The armature spun faster. 4. Optional Activity Pair up with another team and pool your materials. Replace your team’s rubberized magnet with the other team’s coil. Tape the coil in position and connect it to its own battery source. What happens? The armature spun. 1 Write the words motor and electromagnet on the board. Tell the students that they are going to apply what they have learned about the effects of electromagnetism in the previous activity to build a simple motor. 2 Write the word armature on the board. Explain that an armature is a coil of wire in a motor. When electric current passes through the wire coil it creates a magnetic field that interacts with the magnetic field of the permanent magnets in the motor. This interaction causes the armature to move. Explain that a permanent magnet, unlike a temporary magnet, retains or keeps its magnetism for a long time. 426 activity 39 A Simple Motor Additional Information The simple motor constructed in this activity illustrates how continuous motion is possible when the magnetic fields of an electromagnet and a permanent magnet interact. In Activity 40, students will construct a more complex motor—one that functions more like a real motor. © Delta Education. Photocopying and distribution prohibited. Guiding the Activity Guiding the Activity Additional Information Demonstrate for the class how to construct the armature by wrapping the 30-cm (about 1-ft) piece of enamel-coated wire around a rubberized magnet. Slide the coil off the rubberized magnet and loop each end of the wire around the coil two times to hold it together (see Figure 39-1). Gently sand the enamel coating off the entire length of each end of wire, being careful not to deform the coil. This is done so that later, when the armature is inserted into the supports, bare wire will be touching bare wire. 3 © Delta Education. Photocopying and distribution prohibited. 4 Figure 39-1. The armature. Figure 39-2. Supports for the armature. Demonstrate for the class how to make a loop in the middle of a 10-cm (4-in.) piece of bare wire by wrapping it once around a pencil. Two such wires will become the supports for the armature (see Figure 39-2). Distribute to each team a rubberized magnet, two 10-cm (4-in.) pieces of bare wire, a piece of emery cloth, and the 30-cm piece of enamel-coated wire. If needed, assist the students in the construction of the armature and supports. broward county hands-on science Quarter 4 427 Guiding the Activity 5 Additional Information Distribute Activity Sheet 39 to each student, and a base, battery, two electrical clips, two Fahnestock clips, four rubber spacers, four paper fasteners, a piece of masking tape, and the two 25-cm (10-in.) pieces of wire to each team. Have them complete steps 1 and 2 on the activity sheet. Assist students, as needed, in the construction of their simple motors (see Figure 39-3). As necessary, explain that motors are devices that change any kind of energy into mechanical energy, or the energy to make an object move. 6 In the event that a motor does not work, ask, Why do you think your motor doesn’t work well? What would you change to improve how it functions? 7 After students have gotten their motors running, ask, Why does the armature rotate? 428 activity 39 A Simple Motor Figure 39-3. A simple motor. Have the student teams work together to review their setups and compare them with the diagram on the activity sheet. Give the students these tips: a. Make sure that both ends of the armature have been sanded bare and that these bare ends are making contact with the loops of the bare wire supports. b. Check that the paper fasteners are tight enough against the rubber spacers so that the Fahnestock clips make good contact with the bare wire supports. c. Check that the battery is fresh. Remind students that magnets can repel or attract each other. Help students understand that the armature rotates when the magnetic field of the temporary magnet (the wire coil) interacts with the magnetic field of the permanent magnet taped below it. © Delta Education. Photocopying and distribution prohibited. Guiding the Activity Why doesn’t the permanent magnet simply attract or repel the armature? 8 By bouncing in the loops, the armature is constantly making and breaking electrical contact. This electrical “on and off ” produces intermittent electromagnetism in the armature. This is what causes the armature to rotate. Encourage the students to experiment with their motors. Provide whatever additional materials, such as magnets and batteries, they might need. REINFORCEMENT Have the students trace the path of electric current in a simple motor from the negative end of the battery, through each circuit element, back to the battery. Be sure that the path they trace takes into account the interaction between the electromagnetic field of the armature and the magnetic field of the permanent magnet and that this interaction is what causes the armature to rotate. SCIENCE JOURNALS Have students place their completed activity sheets in their science journals. © Delta Education. Photocopying and distribution prohibited. Additional Information CLEANUP Tell the students to disassemble their simple motors and to return the materials to the kit. SCIENCE AT HOME Ask the students to identify some of the small electric motors that are used in the home and to imagine how the tasks would have been performed before the motor was invented. Students may choose hair dryers, blenders, can openers, vacuum cleaners, and so forth. broward county hands-on science Quarter 4 429 Science Challenge Science, Technology, and Society If you or your students have access to small electric motors—such as motors that run toy race cars—that no longer work, let students take them apart. Guide them as needed to identify the parts of the motors that correspond to the parts of the simple motor they built. Store each disassembled motor in a separate container for use in the next Science Challenge. The miniaturization of electric motors has had an impact on scientific research. For example, small, lightweight motors assist in space and undersea exploration. Encourage interested students to investigate how miniaturized motors are used. A transformer increases or decreases the voltage, or “strength,” of an electric current flowing from a power source to an electrical device. Transformers usually incorporate a square loop of iron with two coils of wire on opposite sides of the loop. An electric current flows from a power source into one coil, causing the iron loop to become an electromagnet. The electromagnetism causes electrons to flow in the second coil. If the second coil has more turns of wire than the first coil, the voltage going out of the transformer and to the electrical device is increased; this type of transformer is called a step-up transformer. If the second coil has fewer turns of wire than the first coil, the voltage going out is decreased; this type of transformer is called a step-down transformer. Step-down transformers are commonly used to decrease the voltage for home appliances and toys such as electric trains and slot-car sets. Science Extension Ask students to describe the change in forms of energy that they observed with their simple motor. The chemical energy in the battery is changed to electrical energy, which is changed to mechanical energy— the energy of motion—in the rotation of the armature. Ask students to suggest other forms of energy besides electrical energy that are used to produce motion, and have them give specific examples of such motors. For example, converting chemical energy to mechanical energy (automobiles, lawn mowers, and chain saws). Science and Social Studies Prompt students to try to imagine what everyday life was like before electricity and devices that run on electric motors were available to everyone. What daily tasks would have been more difficult, more timeconsuming, or perhaps even impossible? Have student volunteers role-play the preand post-electricity ways of performing a task. 430 activity 39 A Simple Motor Ask students to identify toys, games, and other devices in their homes that require a transformer to operate correctly. Why is a transformer needed for each device? Encourage students to research how transformers work and the types that are used. How are transformers used in the electric power industry? © Delta Education. Photocopying and distribution prohibited. Connections