How Can You Measure Electrostatic Charge in a DIY Experiment?

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SUMMARY

This discussion focuses on measuring electrostatic charge in a DIY experiment using mica and wool. Gabriel De la Torre seeks guidance on quantifying the charge gained by mica through friction. A recommended method involves using an oscilloscope with a high input impedance of 10MΩ to record voltage traces, which can be analyzed to determine the charge using the formula Q = C * V0. The discussion emphasizes the need for a minimum initial voltage (V0) of 10 mV to achieve measurable results.

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  • Understanding of electrostatic charge and its measurement
  • Familiarity with oscilloscopes and their specifications
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  • Basic principles of RC circuits
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Hello, I needed some help for my physics homework. The aim is to design an experiment that answers the question: Is the number of rubs of a piece of mica (that bag where you put documents to file them or to protect them, often made of plastic. Here is a Pic: http://images.segundamano.com.mx/2011/03/01/6057833/19405116.jpg ) against a piece of wool directly proportional to the charge that it gains? The only thing I'm missing is a way to measure the charge, Could you give me a hand?
Sincerely Gabriel De la Torre
 
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Don't know if this would be sufficiently sensitive, but:
get an oscilloscope with a high input impedance (standard probes are Z = 10MΩ), charge your mica, set the sweep speed to something like 1 us/division, and record the trace: it should look like V0e-t/RC where R = 'scope input Z, C = capacitance between your mica and ground; then V0 = Q/C where Q is the charge you initially put on the mica. All units SI.

You find RC at the time point when the voltage is about 0.37V0.

Example: Z = 10MΩ, C = 1 pF, then RC = 10us = t at 0.37V0, and then Q = 1e-12/V0.

What I don't have a good feel for is how much charge you can get onto the mica. In order for the above to be feasible you would need V0 at least 10 mV (probably; depends on your scope sensitivity), so 1e-2V = Q/1e-12F or Q should be at least about 1e-14 C. That's about 62,000 electrons.




Good luck!
 

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