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Transcript
4th Experimenting with Electromagnets grade Unit: The Practice of Science and Physical Science Sarah Rhodes-Ondi, ELC Naturalist Electricity and Magnetism have many practical uses in everyday life. Can you imagine watching TV at night without electricity? You wouldn’t be able to turn on the TV or a light bulb at night. Electromagnets are very useful because they stop working when the current source is turned off. Telephones, school bells, tape recorders and automatic doors all use electromagnets. How do they work? Let’s start with the basics. Atoms are made up of protons, neutrons and electrons. The protons are positively charged, the electrons are negatively charged and the neutrons are neutral (no charge). The nucleus, center of the atom, is made up of protons and neutrons. The electrons travel around the nucleus in shells. A magnetic field is formed when electrons spin in the same direction around a nucleus (http://www.eia.doe.gov/kids/energyfacts/sources/electricity.html). If they spin in different directions they cancel each other out. Most materials are not magnetic because the electrons spin constantly in many directions and cancel each-other out. Magnets have two polls; a north and a south pole. The magnetic field travels from north to south. An electromagnet is a magnet that is formed due to an electric current. How strong are the magnetic fields formed by an electromagnet? Let’s find out. Steps of the Scientific Method 1. State Problem What question are you trying to answer by doing this experiment? Write “Does an electromagnet pick up objects the same distance away as a standard magnet?” in the spot labeled #1 on your Lab Form. 2. Do Research Read about your topic in books. Talk to experts. Observe the real world. Become the expert! Write anything you learn that will help you plan and explain your experiment on #2 on the Lab Form. 3. State Hypothesis Based on your research, make an educated guess about what will happen when you do your experiment using what you learned from your research (#3 Lab Form). This should be written with a prediction and not in question form. 4. Design Experiment Independent Variable: What factor (treatment) are you testing? Hint: Strength of magnetic field. Dependent Variable: What will you measure or observe? Hint: distance away from object magnet can attract object. Can you think of something else you could measure? Control: What are you comparing the electromagnet to? Hint: standard magnet. Replication: How many replicates will you do? Scientists run a minimum of 5 in case they make a mistake. If you were doing this experiment at home you would need to make 5 different electromagnets and use 5 standard magnets. Hint: Each group is running 1 replicate of this experiment. Record all on Lab Form #4. 5. List Materials Recorded on Lab Form #5. 3 ft of 22 gauge copper wire (for each electromagnet) 1 AA battery (for each electromagnet) 3.5’’ non-galvanized nail (for each electromagnet) Electrical Tape Scissors Ruler Standard bar magnets 3/8’’ * 3/8’’ * 1-7/8‘’ Large Paper Clips Large Insulated Paper Clips 6. Test Hypothesis Procedure: Do experiment! o Record the list of steps below on Lab Form #6. o Create the electromagnet 1. Wrap 40 neat coils around the nail using the middle portion of the wire. Make sure at least ½’’ of the nail is exposed from the point on the pointy end of the nail. 2. Expose one inch of the copper on the ends of the wire using the scissors. 3. Attach ends of the wire to either side of the battery with a small piece of electrical tape. Caution: Copper wire will feel hot to touch! Avoid touching wire when on battery! Pick up electromagnet with battery. o Place the standard magnet at a distance (ex: 2’’, 1’’, ½,’’ 0’’) from the non-insulated paperclip. Record observations. Make note of furthest measurement where magnet attracts the object to it. o Place the electromagnet at all of the same distances as did with the standard magnet. Record observations at each distance. o Record data on Lab Form #7 7. Analyze Results What is the most common distance that each group of students attracted the objects with either magnet? Calculate the mean distance the paper clips are attracted to the magnets for both the electromagnet and standard magnet. Graph your results. Record on Lab Form #8 8. Draw Conclusions (Write answers on Lab Form #9) Does your data support your hypothesis? Which magnet would be better to pick up something further away? Why? What is an advantage of using either type of magnet? What did you learn? How could you change the experiment next time you run it? Try this experiment with the insulated paperclip. What do you observe? Do you have the same results? At home try wrapping the copper wire around a rolled piece of aluminum foil. Is a magnet still formed? Can you think of any other materials to try? Lab Form 1. State Problem 2. Research 3. Hypothesis 4. Design Experiment 5. Materials 6. Test Hypothesis 7. Data Collection (Ask each group for their results to fill in a-e.) a. b. c. d. Observations: Furthest Distance Pick up Paper Clip Electromagnet Standard Magnet e. Calculate the Mean Distance for Each Magnet Type _____+_____+_____+_____+_____ = = 5 _____+_____+_____+_____+_____ = = 5 8. Analyze Results 9. Draw Conclusions References http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magfie.html#c1 http://www.eia.doe.gov/kids/energyfacts/sources/electricity.html http://ktcatspost.blogspot.com/2007/01/homemade-electromagnet-project.html http://van.physics.illinois.edu/qa/listing.php?id=2339 http://education.jlab.org/beamsactivity/6thgrade/magnetsandelectromagnets/over view.html Note to teachers: Explanation The battery is the electric current source, copper is a conductor. By wrapping the insulated copper wire around the nail and connecting it to the battery, the nail becomes magnetic because charge from the current is transferred to the nail. The nail stays magnetized when removed from the current source, so it is important to use different nails each time the kids do the experiment. Class Project Extensions Vary the number of coils. The greater the number of coils, the stronger the field. Test other materials to see if can make a current or not. Sunshine State Standards Benchmarks on next page Plan and conduct an experiment related to electricity and magnetism. Answers how electricity and magnetism are used everyday. Benchmark Science SC.4.N.1.1 SC.4.N.1.4 SC.4.N.1.5 SC.4.N.1.6 SC.4.N.1.8 SC.4.P.8.1 SC.4.P.8.4 Mathematics Description MAFS.4.NF.2.3 Raise questions about the natural world, use appropriate reference materials that support understanding to obtain information (identifying the source), conduct both individual and team investigations through free exploration and systematic investigations, and generate appropriate explanations based on those explorations. Cognitive Complexity: High Attempt reasonable answers to scientific questions and cite evidence in support. Cognitive Complexity: High Compare the methods and results of investigations done by other classmates. Cognitive Complexity: Moderate Keep records that describe observations made, carefully distinguishing actual observations from ideas and inferences about the observations. Cognitive Complexity: High Recognize that science involves creativity in designing experiments. Cognitive Complexity: Moderate Measure and compare objects and materials based on their physical properties including: mass, shape, volume, color, hardness, texture, odor, taste, attraction to magnets. Investigate and describe that magnets can attract magnetic materials and attract and repel other magnets. Cognitive Complexity: High Understand a fraction a/b with a>b as a sum of fractions 1/b. a. Understand addition and subtraction of fractions as joining and separating parts of the same hole.