Download electromagnets, motors, and generators

Name: Jenny Yang Content Area: Physical Science Grade Level: 8th grade Topic(s): Electromagnets, motors, generators and their uses (90 minutes). Standards (Benchmarks): • Materials vary in how they respond to electric currents, magnetic forces, and visible light or other electromagnetic waves. • Electric currents and magnets can exert a force on each other. • Electrical circuits require a complete loop through which an electrical current can pass. • Energy appears in different forms and can be transformed within a system… Electrical energy is associated with an electric current in a circuit… • Energy can be transferred from one system to another (or from a system to its environment) in different ways: …3) electrically, when an electrical source such as a battery or generator is connected in a complete circuit to an electrical device; … Standards (SOL): PS. 1: The student will demonstrate an understanding of scientific reasoning, logic, and the nature of science by planning and conducting investigations in which a) chemicals and equipment are used safely; b) length, mass, volume, density, temperature, weight, and force are accurately measured; j) valid conclusions are made after analyzing data; k) research methods are used to investigate practical problems and questions; l) experimental results are presented in appropriate written form; m) models and simulations are constructed and used to illustrate and explain phenomena PS.11: Students will investigate and understand basic principles of electricity and magnetism. Key concepts include a) Static electricity, current electricity, and circuits b) Relationship between a magnetic field and an electric current c) Electromagnets, motors, and generators and their uses d) Conductors, semiconductors, and insulators Objectives (UKD’s): Understanding: • Students will understand the characteristics of electromagnets. • Students will understand what an electric motor does and their uses. • Students will understand what an electric generator does and their uses. Know: • Students will know that electromagnets use electric current and coiled wires to produce strong magnetic fields. • Students will know that an electric motor transforms electrical energy into mechanical energy. • Students will know that an electric generator uses motion in a magnetic field to produce a current. • Students will know that a generator is a device that converts mechanical energy into •
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electrical energy. Most of the electrical energy we use comes from generators. Students will know that electric motors convert electrical energy into mechanical energy that is used to do work. Examples of motors include those in many household appliances, such as blenders and washing machines. Students will know the similarities and differences between generators and motors and how they function. Students will know the situations in everyday life in which motors and generators are used. Students will know the vocabulary terms for this lesson: electromagnets, motors, generators Students will create an electromagnet and explain how it works. Students will create an electric generator. Students will build a simple motor. Students will build a generator. Topic/Essential Question: What is electromagnetism? Materials & Resources (For each lab group): • Cardboard tubes, 1 narrow and 1 • Iron nail wide • D-­‐cell battery and holder • Coated magnet wire, 16 meters • Container of steel paper clips • Strong magnets • 2 large reshaped paper clips • Scissors • 1 m of enamel-­‐coated 22-­‐24 gauge wire • Plastic vial with cap • Three disc magnets, 10-­‐12 mm • Permanent disk magnet • Neodymium magnets, 10-­‐12 mm • Pliers • Enameled copper wire, 26-­‐32 • Sandpaper gauge • 3 grape-­‐sized pieces of clay • Jumbo LED, 10-­‐mm • 2 wire leads with alligator clips • 1 m insulated copper wire • Electrical tape Safety Considerations: • Hand safety -­‐ Do not cut an object while holding the object in your hand. -­‐ Use a heat-­‐resistant mitt to handle equipment that may be hot. • Sharp object safety -­‐ Use extreme care when handling all sharp and pointed instruments. -­‐ Cut objects on a suitable surface, always in a direction away from your body. -­‐ Be aware of sharp objects or edges on equipment or apparatus. • Electrical safety -­‐ Do not use equipment with frayed electrical cords or loose plugs. -­‐ Fasten electrical cords to work surfaces by using tape. -­‐ Do not use electrical equipment near water or when clothing or hands are wet. -­‐ Hold the plug housing when you plug in or unplug equipment. -­‐ Be aware that wire coils in electrical circuits may heat up rapidly. Engage – Time Estimate: 5 minutes Students will watch a video clip about electromagnets on brainpop. This clip has a quick review on magnets (previous lesson) and it shows the difference between a regular magnet and an electromagnet. It also has a brief introduction to electric motors as well. http://www.brainpop.com/technology/energytechnology/electromagnets/. Explore – Time Estimate: 40 minutes Students will be in their pre-­‐assigned lab groups that I made in the beginning of the year (Note: There are 20 students in this “hypothetical” class and there will be a total of four lab groups with five students in each group). All lab groups will be completing the electromagnet lab. After all four lab groups finish the electromagnet lab, groups 1 and 2 will complete the parts of an electric motor lab and 3 and 4 will complete how generators work lab. Lab groups will be completing these two different labs. They will have 40 minutes to finish both the electromagnet lab and the parts of an electric motor/how generators work lab. See attachments: • Electromagnet • Parts of an Electric Motor • How Generators Work Explain – Time Estimate: 15 minutes I will ask students to share their observations made from the two activities. Students in lab groups 1 and 2 will explain what they saw in the parts of an electric motor lab and students in lab groups 3 and 4 will explain what they saw in the how generators work lab. I will make sure that students cover the important topics and vocabulary. At the end of the discussion, I will give each student the notes that went along with the discussion. See attachment: • Electromagnets, Motors, and Generators Notes Extend – Time Estimate: 25 minutes During this time, students will be making an electric generator. See attachment: • Making an Electric Generator Evaluate – Time Estimate: 5 minutes At the end of the lesson, students will complete a short assessment that will show me if they understand the material. See attachment: • I understand Electromagnets, Motors, and Generators Plans for Diversity: • ADD/ADHD: A variety of activities will be used and students will have opportunities to get up and move around the room throughout the class. •
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ELL: I will help students rewrite the key concepts and have them draw pictures. I will encourage students to use the dictionaries and write the vocabulary definitions in their first language next to the English definitions. Auditory Learners: There will be discussions so that auditory learners will have an opportunity to hear the explanation. Visual Learners: Students will be able to see visually how magnets are connected to wires and batteries to pick up objects (just like a magnet). Kinesthetic Learners: Students will be able to complete the lab activity, which will require them to move around the classroom. Connections: This is the last new lesson of the unit. In this lesson, students will learn about electromagnetics, motors, and generators. This lesson will be easy for students to relate to because motors and generators are always around us and we always use them, so it will be easy for students to think of real-­‐life situations and examples of using motors and generators. Electromagnet (Teacher Copy – Answers are in Red) Procedure: 1. Tightly wrap the piece of insulated copper wire around a nail 10-­‐12 times. 2. Tape one end of the wire to a battery terminal. 3. Hold one end of the nail and touch the other end of the wire to the other battery terminal. Quickly dip the nail into a container of paper clips. Slowly lift the nail above the container. 4. Pull the wire away from the battery terminal and observe what happens. Think It Over: 1. What happened in step 3 when you dipped the nail into the paper clips and then pulled the nail away? Some of the paper clips were attracted to the nail and were lifted up when the nail was pulled out of the container. 2. What happened when you pulled the wire away from the battery in step 4? The paper clips fell away from the nail. 3. What explanation can you give for what you observed in step 3 and step 4? In step 3, the paper clips are attracted by the magnetic field produced by the current in the wire. When the device is disconnected in step 4, the paper clips fall away because there is no current in the coil to produce a magnetic field to attract them. Parts of an Electric Motor (Teacher Copy – Answers are in Red) Procedure: 1. Wrap the wire around the battery. Leave about 5 cm free at each end. Remove the battery. 2. The 2 free ends should be directly across from each other on the coil. 3. Use the sandpaper to scrape the enamel from a 2-­‐cm length at one end of the coil. 4. Use clay to anchor the short ends of the paper clips to the table. Position the clips so that they are standing up with a small U-­‐shapes parallel to each other. 5. Place the free ends of the wire coil in the U-­‐shapes of the paper clips. Make sure the free ends of the wire stick straight out from the coil. 6. Use the remaining clay to anchor the magnet under the wire coil. 7. Attach the alligator-­‐clip end of a wire lead to each of the paper clips. 8. Attach the free ends of the wire leads to the terminals of the battery. Give the coil a gently push and observe what happens next. Think It Over: 1. Next to the name of each motor part, write what you used to make that part (or a similar one) in the motor you just built. a. Brushes: paper clips b. Armature: wire coil c. Commutator: the ends of the wire coil 2. How could you modify this motor to make it do useful work? I could attach small fan blades to it so that the blades would spin and keep me cool. How Generators Work (Teacher Copy – Answers are in Red) Procedure: 1. Using a pair of scissors, gently scrape the ends of the wire to remove the coating. Attach the ends of the wires to the connecting points on the bulb to make a complete circuit. 2. Put three regular disc magnets in the vial. Use the cap to seal the vial. 3. Shake the vial. Observe the bulb. 4. Uncap the vial and switch out the regular disc magnets with the neodymium magnets. 5. Shake the vial again. Observe the bulb. Think It Over: 1. Which variable did you change over the course of this experiment? How did changing the variable affect your observations and results? I changed the type of magnets in the tube. The bulb glowed brighter with the neodymium magnets than the regular magnets. 2. Explain how shaking the tube caused a current to flow in the wire. The changing magnetic field induced an electric current in the wire. 3. Name at least one advantage and at least one disadvantage of a flashlight operated by this kind of generator. An advantage would be that the flashlight wouldn’t need batteries. A disadvantage would be that you’d have to keep shaking the vial in order for the flashlight to stay on. Electromagnets, Motors, and Generators Notes (Both Teacher copy and Student Copy) What Are the Characteristics of Electromagnets (and Solenoids)? • Both solenoids and electromagnets use electric current and coiled wires to produce strong magnetic fields. • A coil of wire with a current is called a solenoid. • The two ends of a solenoid act like a magnet’s poles. However, the north and south poles change with the current direction. • If you place a ferromagnetic material inside a solenoid, the strength of the magnetic field increases. • The material, which has strong magnetic properties, becomes a magnet. A solenoid with a ferromagnetic (highly susceptible to magnetization) core is called an electromagnet. • Both the current in the wire and the magnetized core produce the magnetic field of an electromagnet. This makes the electromagnet’s magnetic field stronger than that of a solenoid. • An electromagnet is a strong magnet that can be turned on and off. • You can increase the strength of an electromagnet in four ways. First, increase the current in the solenoid. Second, add more loops of wire to the solenoid. Third, wind the coils of the solenoid more closely together. Finally, use a material that is more magnetic than iron, such as alnicol, for the core. What Does an Electric Motor Do? How a motor works: the magnetic field around the armature (a loop of wire that current flows through) interacts with the field of the permanent magnet, allowing the armature to turn continuously. The direction of the current determines which way the armature turns. • An electric motor is a device that uses an electric current to turn an axle. • An electric motor transforms electrical energy into mechanical energy. • All motors contain permanent magnets. • Electric motors require an energy source, such as a battery. • Examples of electric motors: blenders, washing machines What Does a Generator Do? How a generator works: A generator uses motion in a magnetic field to produce current. When a crank is turned, an armature rotates in a magnetic field. As the armature rotates, one side of it moves up as the other moves down. This motion induces a current in the armature. Slip rings rotate with the armature. The turning slip rings transfer current to the brushes. When the brushes are connected to a circuit, the generator can be used as an energy source. •
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An electric generator is a device that transforms mechanical energy into electrical energy. Most of the electrical energy we use comes from generators. Example of an electric generators: turbines Making an Electric Generator (Teacher Copy – Answers are in red) Procedure: 1. Carefully wrap 100 turns of coated wire around a wide cardboard tube. 2. Using scissors, carefully strip insulation from the ends of the wires, baring about 3 cm of wire. 3. Connect the ends of the wire to the wires on the galvanometer by twisting them together. 4. With a quick motion, move the magnet into the tube and observe the galvanometer. Make sure the magnet is deep enough to enter the loop of wire. Then, pull the magnet out of the tube. Watch the galvanometer and record your observations. 5. Try different speeds by inserting the magnet faster and slower. What do you notice? The faster the magnet moves, the farther the needle on the galvanometer moves. 6. Try a different magnetic orientation by inserting the magnet the opposite way. What do you notice? The needle deflects in the opposite direction first. 7. Repeat the investigation for the narrow cardboard tube. How does the size of the coils change the reading on the galvanometer? The smaller the coils, the more the galvanometer deflects. 8. Based on your observations, what happens in the wire when you move the magnet through the coils? Electric current flows through the coils. 9. If you wanted to create a powerful generator, how would you construct the coils and the magnet? I would make a generator with very small coils, and I would move the magnet very quickly through them. I understand Electromagnets, Motors, and Generators (Teacher Copy – Answers are in Red) 1. In your own words, define electromagnet. A coil of wire with a current with a core that is highly susceptible to magnetization. 2. What are the four ways to increase the strength of an electromagnet? 1. Increase the current in the solenoid. 2. Add more loops of wire. 3. Wind the coils more closely together. 4. Use a material that is more magnetic than iron. 3. An electric motor transforms electrical energy into mechanical energy. 4. An electric generator transforms mechanical energy into electrical energy. 5. On a scale from 1 – 10 (1 – I have no idea what’s going on, 10 – I can teach my peers) how comfortable are you with this material?