Calculating Capacitor Variance/Uncertainty

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In summary, The question at hand is how to calculate the uncertainty of a charge when given capacitance and voltage across a series and parallel circuit. The question has been adjusted from its original format and an equation has been found to calculate the uncertainty. The uncertainty range can be determined by calculating the minimum and maximum values of the nominal value for both capacitance and charge.
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I can't seem to find out how to calculate a charge's uncertainty when given capacitance & voltage across a series & parallel circuit. Simple circuit setup w/voltage and the 2 capacitors.

Any suggestions?Thanks!
 
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  • #2
Hi Blog,

Could you give somemore details - and what you mean by 'charge uncertainty'?

Thanks

Tom
 
  • #3
Hey Tom,

I had to adjust the question, because it was formatted as a "homework question" so I posted the entire question here: https://www.physicsforums.com/showthread.php?t=126165

Basically, I'm given Capacitance uncertainty(5%) & Voltage uncertainty(1%), as well as the Capacitance & voltage across a simple DC circuit(one Series & one Parallel circuit).

The question was a 2 part, find Q(charge) as well as its uncertainty based on the information above.I finally came across this equation:

(Delta.Z / Avg.Z) = sqrt( (delta.X/avg X)^2 + (delta.Y/avg.Y)^2 )

I was able to find each capacitor's charge uncertainty, except for Q.total's Charge Uncertainty, when using C.eqThanks.
 
  • #4
Hmmm... well, we know c=q/v, so q=cv (obviously not straight out of the problem, but you can calculate the nominal values). I would guess the uncertainty is just the range of uncertainties possible for c and q after that. So you know the nominal value easily, and you can calculate the minimum and maximum values, giving you your uncertainty range
 

1. What is capacitor variance/uncertainty?

Capacitor variance or uncertainty refers to the range of possible values for the capacitance of a capacitor. It is a measure of the degree of uncertainty or error in the measured capacitance value.

2. Why is it important to calculate capacitor variance/uncertainty?

Calculating capacitor variance/uncertainty is important because it allows us to understand the potential error in our measured capacitance values. This is crucial for accurate and precise measurements in scientific experiments and engineering applications.

3. How is capacitor variance/uncertainty calculated?

Capacitor variance/uncertainty is calculated by using the formula: uncertainty = tolerance x measured value. The tolerance value is typically provided by the manufacturer and represents the maximum allowed deviation from the stated capacitance value.

4. What factors can affect the variance/uncertainty of a capacitor?

The variance/uncertainty of a capacitor can be affected by various factors such as temperature, humidity, and frequency. These factors can cause changes in the dielectric material and affect the capacitance value of the capacitor.

5. How can we minimize capacitor variance/uncertainty?

To minimize capacitor variance/uncertainty, it is important to use high-quality capacitors with low tolerances. Additionally, controlling and minimizing the factors that can affect the capacitance value, such as temperature and humidity, can also help reduce the uncertainty in measurements.

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