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Electromagnets Tanya English 8435 Constance Chicago IL 60617 (312) 734-1301 O'Keeffe Elementary School 6940 South Merrill Avenue Chicago IL 60649 (312) 535-0600 Objectives: Grade Level: 3-4 The students will make an electromagnet that will attract a metal object. The students will increase the strength of an electromagnet so that it will attract an increased number of metal objects. The students will compare the properties of magnets and electromagnets. Materials Needed: For 20 students. 10--20 inch strips of insulated copper wire, 1/2 exposed on each end 10--40 inch strips of insulated copper wire, 1/2 exposed on each end 15--size "D" batteries 1--battery holder for 2 "D" batteries 10--compasses 25--iron nails, 4" long 1--box of paper clips, approx. 300 masking or transparent tape iron filings 5" x 7" index card or clear transparency Strategies/Activities: Activity #1: Give each pair of students one battery, iron nail, 40" copper wire, and about 30 paper clips. Have them, using only the nail, try to pick up as many paper clips as possible. Discuss methods and results. Then instruct them to wrap the copper wire around the nail ten times leaving 5-6 inches of wire free on each end of the nail. Attach one end of the wire to the negative pole of the battery. Tape securely and then touch the other end of the wire to the positive pole of the battery while their partner uses the nail to pick up paper clips. Then release the wire from the positive pole of the battery. Discuss methods and results. Record the number of paper clips picked up by the magnetized nail by each group. Concept: Electric current flowing through a wire creates a magnetic field which caused the iron nail to become a temporary magnet. When the electric current is cut off, the nails loses its magnetic property and the paper clips fall off. Activity #2: Elicit ideas and suggestions from students on how they can make the nail pick up more paper clips. Possible ideas are to: 1) use more wire; 2) use more batteries; 3) use more nails. Break students into groups of four and let one group test the idea of using more batteries; another group using 2-3 nails; a third group using more wire, wrapping the nail 15-20 times; and another group wrapping the nail 30-40 times. Reconnect the circuit and pick up as many nails as possible. Record the results of each group and discuss results. Concepts: The strength of an electromagnet can be increased by using more batteries and/or more wires. Using more nails will increase the electromagnet's capacity to hold more paper clips, without necessarily increasing the magnetic force. Activity #3: Have students work in pairs. Give each student a 20" length of wire and a compass in addition to their battery. Have them secure one end of the copper wire to the negative pole of the battery. Have their partner hold the looped center of the wire over the compass and they are to observe what happens to the compass needle when the other end of the wire makes contact with the positive pole of the battery. Repeat this process, but with a slight variation: attach the wire to the positive pole of the battery first, then, holding the looped end of the wire over the compass, complete the circuit touching the other end of the wire to the negative pole of the battery. Observe how the compass needle reacts. Discuss observations. Repeat if necessary. Concept: Electromagnets have poles which can be reversed when the path of electricity is reversed. This is not a characteristic of regular magnets. Activity #4: This is a teacher demonstration in which the students will observe what happens when iron filings are sprinkled over an electromagnet. Place two batteries in a battery holder and connect the end wires to the end wires of an electromagnet (nail wrapped with copper wire). Place them on the overhead projector and place the clear transparency over the electromagnet. Slowly sprinkle iron filings over the transparency and observe what happens to the iron filings. Discuss observations. Concept: Electromagnets have lines of force. Assessments: At the conclusion of the mini-teach, the students will be able to answer thee following questions: Name 3 ways in which magnets and electromagnets are alike. (Have poles, attract metals, have lines of force) Name 3 ways electromagnets differ from magnets. (Electromagnets need electricity to work, the poles of electromagnets can be reversed, the strength of electromagnets can be increased) List 2 ways to increase the strength of electromagnets. (more batteries, more wire) References: Physical Science Activities for Grades 2-8, Science Curriculum Activities Library Tolman, Marvin N. and Morton, James O. Parker Publishing Company, Inc. West Nyack, NY, 1986 Magnetism and Electricity Koch, Dallas Milliken Publishing Co., 1985 Return to Physics Index Electromagnets Shirley Porter-Cesair 2004 So. 13th Ave. Broadview Il 60153 (708) 344-8917 Objective: Charles R. Henderson 5650 So. Wolcott Chicago Il 60636 (312) 535-9080 The students will make an electromagnet and determine the strength of the electromagnet. Materials Needed: Small Compasses Three feet of insulated copper wire per person Six-volt battery Size D batteries Battery Holders Pieces of Cardboard Nails (3 inches or longer) Paper clips, tacks, pins, or other small magnetic objects Iron filings Salad oil Glass or plastic cylinder (100 ml) Wrought iron stand Strategy: Activity 1 Students will work in pairs. Each pair of students will receive a baggie containing materials needed. Allow the students ten or fifteen minutes to explore and manipulate the materials. Have one student from each group connect their compass with wire through the holes in the cardboard. Insert the wire through the Fahnestock clips on both ends. Place the wire over the compass. What happens and why? Concept: The electrical current flowing through a wire will create a magnetic field. This magnetic field causes the needle to turn at a right angle to the wire. Reverse the connections to the battery, thus reversing the direction of the current flow, and the needle will point in the opposite direction. Activity 2 Using the same bag of materials, the pairs of students will begin wrapping the wire around the nail in the same direction until a foot of wire is left at both ends. Insert the end wires into the Fahnstock clips. Hold the electromagnet over a small pile of paper clips, tacks or other small metal objects. How many objects does your electromagnet attract? Take the wire off the battery terminal, and the tacks will immediately fall off. Concept: The current passing through the wire produces an invisible magnetic field. When the current is cut off, the magnetic field disappears, then the molecules of the iron return to their helter-skelter position and the nail loses most, but not all, of its magnetism. Performance Assessment: As a result of the electromagnet mini-teach, the sixth grade students will be able to describe the characteristics of a magnet and an electromagnet. Both attract metal and have magnetic fields; the electromagnet needs an electrical current. The students will be able to make an electromagnet with a wire, a battery, and a nail. The students will be able to test the strength of the electromagnet by using more coiled wire and additional batteries and nails. Conclusions: In activity 1 we found that electricity can produce magnetism and magnetism can produce electricity. The opposite ends or poles of magnets are attracted to each other and like ends repel. In activity 2 we found that current through a wire produces an invisible magnetic field. When the current is cut off, the magnetic field disappears, then the molecules of the iron return to their helter-skelter position and the piece loses most, but not all, of its magnetism. References: Safe and Simple Electrical Experiments. Rudolf F. Graf. Publications, Inc.,N.Y., 1964. pps. 86-88 and 93-94. Be a Kid Physicist. William R. Wellnitz, Ph.D., Hill, Inc., Blue Ridge Summit, PA. 1993. p, 82. Dover Tab Books. McGraw- Science Projects About Electricity and Magnets. Enslow Publishers, Inc., N.J., 1994. pps. 72-82. Return to Physics Index Robert Gardner.