The Norwood Science Center. Energy Grade 4

Transcription

1 The Norwood Science Center Energy Grade 4 Background Information: Whenever an electric current goes through a wire, a magnetic field is created around the wire. Electricity and magnetism are related; an electric current produces a magnetic field, and a change in a magnetic field can produce an electric current. When current goes through a coiled wire, the magnetic field is strengthened because each coil acts like a separate magnet. The strength of an electromagnet can be increased in several ways. The number of coils can be increased. The voltage of the current going through the wire can be increased. Using a metal core, such as a nail or a bolt, will also increase the strength of the electromagnet. The magnetic field produced by the current in the coils induces a magnetic field in the iron core. Electromagnets are an integral part of many common devices such as telephones, electric motors, buzzers, generators, televisions, and doorbells. Electromagnetism Gr. 4 Page 1 of 5

2 TITLE: ELECTROMAGNETISM PURPOSE: MATERIALS: Build an electromagnet Increase the strength of the electromagnet (per pair of students) 6 volt battery (1) Tray #1 Paper clip target (1) Paper clips (100) Tray #2 Buzzer (1) Red Alligator clip wire (1) Doorbell switch, wired (1) Two insulated wires, w/stripped ends (2) Nails (2) NSC Coil (1) Procedure: 01. Group students. 02. Distribute trays and 6-volt battery. 03. Place Figure 1 on the board. Instruct the students to wire the circuit with V = 6 volt battery, S = momentary switch and R = buzzer. It will be important for the students to wire the black wire of the buzzer to the negative terminal of the battery. An easy way to do this is to connect the green wire on the switch to the negative terminal of the battery; then the black wire of the switch will be negative (attaches to the black wire of the buzzer). One end of the red alligator clip wire is connected to the positive terminal of the battery. The other end of the red alligator clip wire is connected to the red wire of the buzzer. Electromagnetism Gr. 4 Page 2 of 5

3 V S R Figure To check the circuit, students need to leave the momentary switch on the desk, and push down on the button (so commonly misnamed the doorbell, the button is the doorbell switch) to allow the buzzer to buzz. Students cannot continue until they can operate the buzzer by use of the momentary switch. 05. At this point the students are to remove the buzzer and return it to the Tray # Each student is to obtain a single piece of insulated wire and a nail. 07. Students are to wrap the wire around the nail ten times. The wraps are to be tight and all running in the same direction. The pieces of wire coming off the nail should be parallel. See Figure 2 below. Figure 2 Electromagnetism Gr. 4 Page 3 of 5

4 08. Students are to place one of the 10-wrap coils into the circuit. They are to place the coil into the circuit where the buzzer was earlier in the lesson. 09. Tray #1 is placed near the coil. The target is removed and placed under the coil. 10. One student is to hold the coil by the parallel wires over the tray of paper clips. 11. The second student places a finger (the index finger works well) over the momentary switch. 12. The teacher counts down to zero, the momentary switch is closed (the button pushed and held down) and the coil is placed down on the clips and moved around. 13. The teacher allows the coils to drag on the clips for five seconds, and tell the students to hold the coil over the target. 14. Students release the momentary switch, allowing the paper clips attracted to the coil to fall to the target. Any stray clips that hang on the coil should be removed and added to those on the target. Students should close the switch for the shortest period of time. since there is no resistor, the circuit is a short circuit. This will allow the circuit to generate heat if electricity is allowed to flow for an extended period of time. 15. Students count the clips on the target. 16. Students record in their book the number of clips held by the coil and the number of wraps in the coil. 17. Students return the clips to Tray #1. Electromagnetism Gr. 4 Page 4 of 5

5 18. The second coil is given 5 more wraps for a total of 15 wraps. 19. The 10-wrap coil is replaced with the15-wrap coil. 20. Students repeat the procedure to find how many clips 15-wrap coil lifts. 21. Students are to replace the 15-wrap coil with the NSC 25 wrap coil. The procedure is repeated once again. 22. When completed the students return the materials to the original condition. 23. Students graph clips held by coil wraps. 24. Students are to determine if there is a pattern of note in the data. Electromagnetism Gr. 4 Page 5 of 5