Physics Demo Manual

Demonstrations are cataloged according to PIRA Bibliography

PLEASE REQUEST DEMOS WELL IN ADVANCE

Due to Physics Building renovations, the lead time to set up demo requests has increased due to the need to transport equipment across campus. Please be kind and let me know well ahead of time what you need.

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Mechanics
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Harmonic Motion
Waves
Acoustics
Instruments: Sonometer; Open / Closed Resonance Tube; Resonant tunning fork; video - Dancing Flames (Ruben's Tube); video - Air Driven Organ Pipe; Singing Tubes and Rods; Chladni Figures; video - Breaking a Wine Glass

video - Dancing Flames (Ruben's Tube)

Purpose:

Use flames to visualize the nodes and antinodes of standing waves.

Procedure:

DEMO VIDEO DOWNLOAD w/ sound / 1920x1080 / 24.19Mb/s / 567MB size
DEMO VIDEO DOWNLOAD w/ sound / 854x480 / 5.69Mb/s / 130MB size

A long tube with a line of holes is filled with methane gas and driven at the open end with a loudspeaker. Once the pressure inside the tube is sufficient, the flames over the holes can be lighted.

place tube with stands onto lecture bench
connect plastic tubing to classroom gas source
fully open gas valve
wait about 30 seconds, then start lighting the flames w/ lighter
over time, the flames will increase a little as the air gets flushed out

When using a PASCO function generator, frequencies in the 600 - 1300 Hz range is best. Use an amplitude of about 1V to 2V peak-to-peak. The height of the flames indicates nodes and anti nodes of the standing wave. Alternatively if driven with music the flames will dance synchronously with the music.

Hints:

For simple standing waves use PASCO generator to drive the speaker directly.

REFERENCE: Physics Teacher Vol.17, 306 (1979)