Untitled Document

Physics Demo Number: 126

Approximate

Run Time: 5 min

Resonance in An Open Tube Induced by A Noisy Heat Source

Demo Description

One lights a burner and lowers a vertical ceramic tube over the burner to obtain a very loud noise akin to a steamboat whistle.

Scientific Principles

Tuned tube amplification of hydrodynamic instability noise in a burner's properly adjusted flame.

Equipment

Ceramic Tube
Fisher Burner
Gas supply

Equipment Location

The Ceramic Tube and Fisher Burner are on the lower shelf of the cart for demo(034).

That cart is along the back corridor of the prep room on the left wall .

The gas supply is the spigot on the lecture table.

Instructions

The ceramic tube and the lit Fisher burner ( adjusted for a properly noisy flame ) are used to show resonance induced by rising hot air in an open ended tube.

When the tube is held vertically and lowered concentrically and carefully over the lit Fisher burner, a sharp resonance sounding somewhat like a steamboat whistle will be emitted when the end of the tube is a few inches above the bottom of the burner.

Care must be taken to avoid setting the tube on fire. Also the flame may go out and leave the gas escaping, so one must promptly remove the tube and check the state of the burner if the sound quits, or never starts.

Open flames and gas are very dangerous and should be treated with great respect, both for the safety of the lecturer and of his/her students.