Physics Dept. Demonstration Manual

DVW17 - Vibrating Wire

Objective:

To illustrate the relationship between wavelength, frequency and harmonics.

 
Apparatus:  
  • Long (2 meter) steel wire support board
  • Custom loudspeaker
  • Audio amplifier
  • Signal generator
  • Clamps - 2 large, 1 small
  • Long leads
  • Coax cable, BNC/RCA
  • 1 kg mass


Method:

Hang the 1 kg mass on the free end of the wire. Align the speaker assembly and clamp to the base.

Set the signal generator to less than 100 Hz. Set the amplifier volume to about 2 on dial.

Turn on everything. Adjust frequency to produce a half wave from end to end.

Slowly increase frequency to create vibration patterns of 2, 3, 4 multiples. If desired, increase the mass and repeat.

The observed vibration patterns are quite graphic.

Note:

Do not overdrive the speaker cone. Make sure the "OFFSET" of signal generator is zero. Do not overload the wire with too high a value of mass.