Physics Demo Number: 034

Approximate Run Time: 10 min

Flame Tube For Compressional Standing Sound Wave

Demo Description

Use a dedicated flame tube on a cart.

One may implement compressional standing waves in the gas in the tube by means of the attached function generator and acoustic speaker which are coupled to the gas column.

By tuning the function generator , one can generate standing waves in the gas column corresponding to a variety of numbers of loops.

The patterns seen  in  the tips of the flames are sine waves. The length of a flame at a given hole depends on the state of the gas beneath it, which varies as the speaker driving frequency varies.

Scientific Principles

• Longitudinal Standing Sound Waves

Equipment

• A dedicated cart with dedicated attachments:  a sound tube, a function generator and a butane tank. 

Equipment Location

• The cart lives in the Prep Room along the back hall left wall.

Instructions

The photos show the equipment in use with the standing wave in the tube evidently having a wavelength of about half the tube length.

One needs to exercise great care in using this apparatus and NEVER leave it unattended.

Take care to ALWAYS have it very near the center of your attention while the flames are going. 

Notice that there are two gas shut off valves involved with the gas source.

Writeup created by David A. Burba

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