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Code Number: 5F30.60
Demo Title: Relaxation Oscillators - Neon Bulb, Doorbell, and Strobe Lights
Condition: Excellent
Principle: Relaxation Oscillators
Area of Study: Electricity and Magnetism
Equipment:
Neon Bulb Relaxation Oscillator Circuit, Variable Strobe Light Kits.
Procedure:
Connect the DC voltage source and turn up to the voltage indicated. The neon bulb should flash with a rate of 2 to 5 seconds. Changing the size of the resistor will change the time of oscillation.
The variable rate strobe units are the same as the neon circuit in that a capacitor charges and at some threshold voltage the strobe bulb triggers. The capacitor voltage then falls and starts to recharge to the threshold voltage again. The potentiometer control varies the resistor value and thus changes the charging time.
A simple homopolar motor is made by attaching a magnet to the negative end of a AA battery and dropping the spiral copper spring over the battery. Place a small dimple in the positive pole of the magnet to keep the spring centered while it rotates. Observe the rotating coil closely and you will see it jump up and break contact repeatedly due to the slight contractions of the spring like coil when it is energized.
We have a variety of relaxation oscillators available. Look at these webpages:
3A95.10 - Relaxation Oscillators
6-00.00 - Stroboscope (we have small variable frequency strobe lights available).
2B60.30 - Tantalus Cups
3D32.15 - Stadium Horn
4C30.25 - Geyser
4C31.30 - Drinking Bird
4C31.37 - Franklin's Pulse Glass Engine
5A40.70 - Kelvin Water Dropper
5F30.60 - Relaxation Oscillators - Neon Bulb, Doorbell, and Strobe Lights
10A06.10 - Relaxation Oscillators
13A10.10 - Perpetual Motion
References:
- Stanisław Bednarek, "Amazing Vibrations Within the Homopolar Motor", TPT, Jan. 2018, Vol. 54, #1, Jan. 2018, p. 47.
- George M. Caplan, "Simple DC Power Supply", TPT, Vol. 46, #1, Jan. 2008, p. 57.
- Paul Chagnon, "Animated Displays V: Relaxation Oscillators", TPT, Vol. 32, # 7, p. 432- 436, Oct. 1994.
- Richard Crane, "What Does the Drinking Bird Know About Jet Lag?", TPT, Vol. 27, #6, Sept. 1989, p. 470.
- Earl M. Sawyer, "The Perpetual Light", TPT, Vol. 10, #7, Oct. 1972, p. 362.
- Zenon Gubanski, "Capacitance by Relaxation Oscillations", TPT, Vol. 9, #2, Feb. 1971, p. 105 & TPT, Vol. 41, #2, Feb. 2003, p. 123.
- Paul J. Ring, "Lecture Demonstration of the Validity of the Rules for Finding Equivalent Resistance and Capacitance", AJP, Vol. 46, #7, July 1978, p. 762.
- James H. Vignos, "Comment on: 'Relaxation Oscillators: Electrical and Water'", AJP, Vol. 40, #2, Feb. 1972, p. 360.
- Leonard Finegold, "Relaxation Oscillators: Electrical and Water", AJP, Vol. 39, #5, May 1971, p. 575.
- D. Rae Carpenter Jr. and Richard B. Minnix, "E-240. Relaxation Oscillator", DICK and RAE Physics Demo Notebook, 1993.
- D. Rae Carpenter Jr. and Richard B. Minnix, "E-400. Relaxation Oscillator w/Scope", DICK and RAE Physics Demo Notebook, 1993.
- E-4f: "A Flashing Neon Light", Wallace A. Hilton, Physics Demonstration Experiments, p. 73.
- Robert L. Wild, "150: RC Circuit-Relaxation Oscillator", Low-Cost Physics Demonstrations, p. 88.
- "The Neon-Tube Relaxation Oscillator", The Physics Instructional Resource Association (PIRA) Newsletter, Vol. 3, #3, May 1988, p. 2.
- Forrest M. Mims, "The Neon Glow Lamp", Experimenter's Corner, Dec. 1976, p. 111.
Video Credit: Jonathan M. Sullivan-Wood.