PURPOSE: To demonstrate standing sound waves in air excited by convection currents.
DESCRIPTION: A switch is held closed, activating a nichrome wire coil in a vertical glass tube, leading to a very loud roar at about 130 Hz, the fundamental frequency of a four-foot air tube. This is the classic Rijke tube demonstration with an electrical heater replacing a gas burner and screen as the source of the convection currents.
SUGGESTIONS: See Demonstration H3-13: ROARING TUBE - 8 FT for a MUCH more dramatic version of this, using an 8-foot tube with a fundamental frequency of around 70 Hertz. See Question of the Week #303 for information on using this demonstration to enhance class involvement.
REFERENCES: (PIRA 3D30.70) See Demonstration Reference File for further information about the theory and practice of Rijke tubes.
Click here for close-up photograph of our nichrome heater coil in the glass tube of this demonstration, or click here for a mechanical drawing of the heater element.EQUIPMENT: Glass tube with heater installed on rolling stand.
SETUP TIME: None.
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