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How is electric charge measured?

  1. Apr 29, 2012 #1
    How do we measure the amout of charge body has. Can you tell me some instruments and how do they work.
    Well i know how ampere is defined so one coloumb will be the current that flows in one second - but how can wemeasure that?
     
  2. jcsd
  3. Apr 30, 2012 #2

    Drakkith

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    Staff: Mentor

  4. Apr 30, 2012 #3
    Its good to test if charge is present as the leaves will repel but how do you measure the amount of charge?
    Perhaps i dont understand -
     
  5. Apr 30, 2012 #4

    mfb

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    2016 Award

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    More charge => more force between the leaves => larger distance between them

    The basic idea is that you convert the measurement of the charge to a measurement of some other property - like the distance between the leaves, or a current somewhere, or an acceleration of particles or whatever.
     
  6. Apr 30, 2012 #5
    one technique is to transfer the charge to a known capacitor then measure the voltage across the known capacitor. Then use Q = C x V to find Q.
    An instrument designed to do this is called an electrometer.
    If you want to measure the charge on a capacitor then a vibrating switch can be used to alternately charge the capacitor from a battery then discharge it through a milliammeter. If the frequency of switching is known then the chatge transferred at each switching can be calculated from the current read by the milliammeter.
     
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