Electromagnet Category: Physics: Electricity & Magnetism Type: Class Experiment (1 hour) Rough Parts List: 1 1 Long nail Cork Magnet wire, or small gauge vinyl 36” insulated wire 1 Small piece of foil 5-­‐10 Paperclips 5-­‐10 Thumb tacks 1 Small piece foil Electrical tape Tools List: Wire cutter Sandpaper Video: http://youtu.be/EmAcuQTSRGk How To: Pick up the nail and try to lift a paper clip or thumb tack with it. Push the sharp end of the nail into a cork. © 2013 Mission Science Workshop. All Rights Reserved worldwide. When linking to or using MSW content, images, or videos, credit MUST be included. Cut approximately three feet of wire. Leaving approximately 6” of free wire, wrap the wire around the nail. Keep count of the number of wraps around the nail. Every few loops that you make around the nail, push the wire up the nail to form a tight coil. Continue this “wrapping and pushing” technique until the entire nail is covered. Leave a 6” tail of free wire at the bottom. Tape a battery to the cork using electrical tape. Use sandpaper to remove approximately 1” of varnish insulation from both wire ends. The wire will change color when the insulation is removed. © 2013 Mission Science Workshop. All Rights Reserved worldwide. When linking to or using MSW content, images, or videos, credit MUST be included. Tape the top tail of copper wire to the top of the battery. Make a loop in the bottom tail of wire. Cover the loop with foil, fold it in half with the wire inside it. The wire covered in foil acts as a switch; when pressed to the battery the electromagnet turns on. With the electromagnet on, try lifting the paperclip with the nail again. Experiment with the strength of the electromagnet by increasing and decreasing the number of wraps around the nail. Try picking up different objects with the electromagnet. Does the number of wraps influence the strength of the magnet? Fine Points: © 2013 Mission Science Workshop. All Rights Reserved worldwide. When linking to or using MSW content, images, or videos, credit MUST be included. → The bottom wire can also be taped to the battery. To turn off the battery just remove the tape and move the wire away from the battery. → Depending on the strength of the battery and the size of the wire, the electromagnet may get hot if left on for a while; it means the battery is dying and may cause small burns. → You may also try bunching the coil of wire on top of itself near the head of the nail instead of covering the length of it, to see which works better. → Experiment with the strength of the electromagnet by increasing and decreasing the number of wraps around the nail and try picking up the same object Objectives: During this activity students will: 1. Learn to build an electromagnet. 2. Understand that an electric current creates a magnetic field. 3. Understand that the number of turns of wire can affect the strength of an electromagnet. Concepts Involved: •
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Magnetism and electricity are closely related phenomena. Electric currents produce magnetic fields. Different factors affect the strength of electric and magnetic forces. Focus Questions: 1. Does the number of times you wrap the wire around the nail affect the strength of the electromagnet? 2. Does the thickness of the wire affect the strength of the electromagnet? 3. Does the size of the nail effect the strength of the electromagnet? Elaboration: For a long time it was thought that magnetism and electricity were not related. However, in 1820 a Danish scientist named Hans Christian Oersted noticed a magnetic compass move when he turned on a circuit next to it. Later, the work by Michael Faraday and James Clerk Maxwell showed that they are aspects of the same force, now called the electromagnetic force. Electric and magnetic forces can be detected in areas called electric and magnetic fields. Moving electric fields can produce magnetic fields and changing magnetic fields can produce electric fields. This is the basis for understanding electromagnets. In electromagnets, a magnetic field is induced by the flow of an electric current through a coil of wire. As the current flows it creates a magnetic field around the coiled wire, and magnetizes the metal. Electromagnets are useful because you can turn the magnet off; when the flow of electricity stops, the magnetic field disappears. The strength of the magnet is directly related to several things: the number of times the wire is wrapped around the core, the material of the core, the distance from the core to the wire, and the current flowing through the wire. To create a stronger magnetic field, the wire can be more tightly wrapped to decrease the distance from the current to the core. Also, the more loops the current makes around the core the stronger the magnetic field. In the above experiment we used an iron nail for the core. Iron is ferromagnetic, meaning that it can be magnetized in a magnetic field. Cobalt and nickel are also ferromagnetic. There are many examples of electromagnets in your home, such as, doorbells, speakers and electric motors. Links to k-­‐12 CA Content Standards: Grades k-­‐8 Standard Set Investigation and Experimentation: © 2013 Mission Science Workshop. All Rights Reserved worldwide. When linking to or using MSW content, images, or videos, credit MUST be included. Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other strands, students should develop their own questions and perform investigations. Grades k-­‐12 Mathematical Reasoning: 1.0 Students make decisions about how to approach problems: 1.1 Analyze problems by identifying relationships, distinguishing relevant from irrelevant information, sequencing and prioritizing information, and observing patterns. 1.2 Determine when and how to break a problem into simpler parts. 2.0 Students use strategies, skills, and concepts in finding solutions: 1.1 Use estimation to verify the reasonableness of calculated results. 1.2 2.2 Apply strategies and results from simpler problems to more complex problems. 1.3 Use a variety of methods, such as words, numbers, symbols, charts, graphs, tables, diagrams, and models, to explain mathematical reasoning. 2.5 Indicate the relative advantages of exact and approximate solutions to problems and give answers to a specified degree of accuracy. 3.0 Students move beyond a particular problem by generalizing to other situations: 3.1 Evaluate the reasonableness of the solution in the context of the original situation. 3.2 Note the method of deriving the solution and demonstrate a conceptual understanding of the derivation by solving similar problems. 3.3 Develop generalizations of the results obtained and apply them in other circumstances. Grade 4 Standard Set 3. Earth Sciences Electricity and magnetism are related effects that have many useful applications in everyday life. As a basis for understanding this concept: 3.a. Students know how to design and build simple series and parallel circuits by using components such as wires, batteries, and bulbs. 3.b. Students know how to build a simple compass and use it to detect magnetic effects, including Earth’s magnetic field. 3.c. Students know electric currents produce magnetic fields and know how to build a simple electromagnet. 3.d. Students know the role of electromagnets in the construction of electric motors, electric generators, and simple devices, such as doorbells and earphones. 3.e. Students know electrically charged objects attract or repel each other. 3.f. Students know that magnets have two poles (north and south) and that like poles repel each other while unlike poles attract each other
© 2013 Mission Science Workshop. All Rights Reserved worldwide. When linking to or using MSW content, images, or videos, credit MUST be included.