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OHM'S ZIP LINE
Presenter: Rick Frutuozo,
Thomas Harrison Middle School, rfrutuozo@harrisonburg.k12.va.us
Va. SOL:
PS 11: The student will investigate and understand basic principles of electricity and magnetism.
Topic/Concept
Key concepts include static, current, and circuits.
Topic/Concept Resistance in electric circuits; High resistance will result in dim lighting circuits; principles of light dimmers and audio volume controls.
Materials
2- 6 volt lantern batteries or equivalent.
Several alligator clips.
1- 6 volt mini lamp and socket.
30ga nichrome wire.
2- Ringstands and clamp
Safety Considerations
Include all safety issues
Should a student bypass the lamp, the wire has the potential to heat rapidly and can burn.
Presentation
As the back of the alligator clip is slid along the wire toward the lamp, it grows brighter, as it is moved away, dimmer. Simply set up a circuit through the nichrome wire with the alligator clip's back sliding on the wire. The lamp socket is fastened in the clamp at one end of the wire at the top of one stand, and the wire end is about five feet away at top of the other stand. Students seem never to tire of this one!! The greater the distance between the stands, the more effective the demo. Try to get the lamp to go from being totally dim to very bright! (A darkened room makes this even more "cool").
 
How the physics is demonstrated
As the alligator clip is slid away from the lamp, the resistance is increased resulting in a dimmer lamp.
As the alligator clip is slid toward the lamp, the resistance is decreased resulting in a brighter lamp.
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