Solving for Time Elapsed in an RC Circuit

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SUMMARY

The discussion focuses on calculating the time elapsed in a charging RC circuit when the capacitor reaches 80.0% of its final charge. The relevant formula for capacitor charging is identified as an exponential function involving time (t) and the product of resistance (R) and capacitance (C), represented as τ (tau). To find the time elapsed, one must set the final charge to 100% and the charge at time t to 80%, leading to a solution for t that is likely between 1*RC and 2*RC.

PREREQUISITES
  • Understanding of RC circuit fundamentals
  • Familiarity with exponential functions
  • Knowledge of capacitor charging equations
  • Basic algebra for solving equations
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  • Study the formula for capacitor charging in detail
  • Learn about the time constant τ in RC circuits
  • Explore the implications of different percentages of charge in capacitors
  • Investigate real-world applications of RC circuits in electronics
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Students studying electrical engineering, educators teaching circuit theory, and hobbyists interested in electronics and circuit design.

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Homework Statement



For the following questions, consider a charging RC circuit, and let the time constant be represented by τ.
How many time constants have elapsed when the capacitor has 80.0% of its final charge?

Homework Equations


I have no clue! i just need a nudge.


The Attempt at a Solution

 
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You need the formula for how a capacitor charges as a function of time.
I recall it is exponential with a t/(RC) in the exponent. Likely you can find it in the Wikipedia article for "capacitor" if you don't have it handy.
Once you have the formula, set the final charge to 100 and the charge at time t to 80. Then solve for t. It should come out to 1*RC or 2*RC (more likely something in between).
 

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