Abstract
Add sine waves to make a square wave.
Portable
Yes
Principles Illustrated
Any wave can be made by adding sines and cosines together. Here we add sine waves to make a square wave at least approximately.
NCEA & Science Curriculum
Extensionw
Instructions
The following commentary relates to an existing demo at VUW but it can provide the basis of a demo for teachers to try in the classroom.
The simulator will launch running. Adjust the amount of the fundamental and harmonics needed to match the square wave. Note: square waves have very high frequency components. Even including the correct amounts of all frequencies up to the 15th harmonic will not accurately reproduce the square wave. There will still be wiggles in the high and low states and the rising and falling edges will be sloped. The fact that one cannot reproduce the vertical rise and fall without infinite frequency components is educational. Point out to students that any very sharp (rapidly varying) features in the waveform contain high frequencies. The answer: mix in the fundamental, 1/3 as much of 3f, 1/5 as much of 5f, and so on. Even multiples of the fundamental frequency will take you further from a square wave (also educational).
SYSTEM REQUIREMENTS
Requires at least an XGA display (1024 x 768).
The Wave Simulator app is small, but the LabVIEW Run Time engine requires significant space on your drive.
Safety
Individual teachers are responsible for safety in their own classes. Even familiar demonstrations should be practised and safety-checked by individual teachers before they are used in a classroom.
Related Resources
Combining Sounds
Teaching Resources
Would you like to contribute lesson suggestions? Contact us.
Credits
This teaching resource was developed with support from
The MacDiarmid Institute
Faculty of Science, Victoria University of Wellington
School of Chemical and Physical Sciences, Victoria University of Wellington