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Doubt in Piezo-electricity

  1. Jul 5, 2013 #1

    What would be the voltage developed across a Piezo-electric crystal, say Quartz of size 15 cm-length, width and 2 cm thickness, If I stand on it. My weight is around 75 kg :)

    I have no idea how to calculate it.
  2. jcsd
  3. Jul 5, 2013 #2


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    Gold Member

    That depends on the type of crystal. Some examples are given for Barium Titanate, one of the most common, here: http://en.wikipedia.org/wiki/Piezoelectricity

    I don't know how or where to find the information you ask for.
  4. Jul 6, 2013 #3


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    Staff: Mentor

    That sized crystal is probably useful only as a doorstop. :wink:
  5. Jul 6, 2013 #4


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    Young Learner,

    There is a way you could find the voltage generated by your weight on that quartz slab: measure it!

    A biologist here in Brasil told me that certain insects, especially some ant species, were attracted by electrostatic fields. I amassed more than 100 rose quartz crystals and built a large circular arch with them using silicone adhesive to steady the individual crystals. This configuration caused the bottom-most crystal to be under the most physical stress owing to the weight above it, and thereby generated a large electrostatic field. The effect decreased all the way to the uppermost "keystone" crystal at the top center of the arch. I set the arch out in my yard and waited. Soon a large swarm of army ants passed through my yard but did not seem to loiter on or around my arch. Later, leafcutter ants carrying leaf parts back to their underground fungus gardens stopped and lingered at the base of the arch. For weeks some of the leafcutters milled about the base of my quartz crystal arch. My observations are: the arch was electrically charged, higher voltage at the base. Those ants noticed it and seemed to like it.

    Perhaps you could place your quartz slab outside, place a heavy weight on it, and see if it attracts ants.
  6. Jul 6, 2013 #5

    1. How much voltage did your electricity develop?

    2. How much did the quartz crystal cost you?
  7. Jul 6, 2013 #6


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    Gold Member

    You are welcome. I never put my digital voltmeter onto the crystals under stress, so I can't answer that.

    I bought the beautiful pink (rose) quartz crystals directly from the miners who dug them out of the mountainsides in North Central Brasil. What I paid those miners would not be relevant unless you lived nearby.

    You can find lots of quartz crystals for sale at mineral shows. The closer to the source, the cheaper they are!

    Read up here! Nearly everything anyone would want to know about quartz deposits, etc. world-wide: http://www.minsocam.org/msa/collectors_corner/arc/quartzdep.htm
    Last edited: Jul 6, 2013
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