How is electric charge measured?

[jd12345]

How do we measure the amount 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?

 

[Drakkith]

Here's one way: http://en.wikipedia.org/wiki/Electrometer

 

[jd12345]

Its good to test if charge is present as the leaves will repel but how do you measure the amount of charge?
Perhaps i don't understand -

 

[mfb]

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.

 

[truesearch]

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.