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===== Pressure Wave Simulation: Instructor's Guide =====



==== Main Ideas ====
  * Relationship between voltage and charge
  * Relationship between pressure and displacement waves
  * Reflection and transmission coefficients
  * Sinusoidal functions


==== Students' Task ====
//Estimated Time: 5 minutes//

Students are presented with a picture of molecules at three successive times and asked to draw both the displacement and pressure graph that would represent the picture. A Mathematica simulation of the situation is used to summarize the discussion.

==== Prerequisite Knowledge ====

  * Sinusoidal functions.
  * Derivative relationship between pressure and displacement


==== Props/Equipment ====

  * Small White Boards
  * Computer with Mathematica

==== Activity: Introduction ====

This activity begins with a SWBQ where students are presented with a picture of molecules of molecules at three successive times and asked to draw both the displacement and pressure graph that would represent the picture.{{ activities:content:photos:wvpressurewavesimtask.jpg?350 }}


==== Activity: Student Conversations ====
  * **What are the dots?** -- there are several analogies to help the students think about what the dots represent:
    * electrons in a coaxial cable
    * air molecules in a pipe
    * people in class (see [[courses:activities:wvact:wvpressurewave|Creating a Pressure-like wave in a Coaxial Cable]] activity)
  *  **What kind of a wave is this?** -- answers such as longitudinal and traveling can lead to good conversation.


==== Activity: Wrap-up ====
Things to emphasize in the discussion:
  * the connection of displacement, force, and pressure to charge, current, and voltage,
  * the derivative a sinusoidal function is itself a sinusoidal function and also satisfies the wave equation and have reflection and transmission coefficients,
  * the sign difference between the reflection and transmission coefficients for displacement and pressure waves,

==== Extensions ====

This is a good follow-up activity to the [[courses:activities:wvact:wvpressurewave|Creating a Pressure-like wave in a Coaxial Cable]] kinesthetic activity. 

Together, these two activities provide an excellent set up for the [[[courses:activities:wvact:wvcoaxlab| Wave Propagation in a Coaxial Cable]] lab.