Understanding the Formula for Exponential Decay of Voltage

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Discussion Overview

The discussion revolves around understanding the formula for calculating the time during the exponential decay of voltage, specifically the expression t=T1n(E/Vl). Participants are seeking clarification on the application of the formula and the role of the natural logarithm in the calculations.

Discussion Character

  • Technical explanation, Homework-related

Main Points Raised

  • One participant requests help in understanding the formula t=T1n(E/Vl) and how to apply it to a specific example.
  • Another participant points out that "1n" is actually the natural logarithm (LN) and suggests it is a function on scientific calculators.
  • A participant expresses frustration that their calculations do not yield the expected result.
  • Another participant confirms the calculation method, stating that multiplying the natural log of the voltage ratio by 7.5ms yields approximately 2.38ms.
  • A later reply acknowledges the assistance received.

Areas of Agreement / Disagreement

There is some agreement on the formula's application, particularly regarding the use of the natural logarithm. However, there is disagreement regarding the accuracy of the calculations, as one participant claims their results do not match the expected outcome.

Contextual Notes

Participants have not fully resolved the discrepancies in calculations, and there may be assumptions about the values used in the formula that are not explicitly stated.

bryanehli
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Please Help!

This is based on the time at any point on the curve during exponential decay of voltage.

Could someone explain to me this formula?

t=T1n(E/Vl)

example:

t=(7.5ms)1n(20v/14.57v)=2.38ms.

I get 20/14.57=1.372683596
(7.5)(1.372683596)=10.29512697
where and how do you get 2.38, where does the 1n fall in and how? is there a numerical value for this statement? Please help?
 
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Please don't multiple post the same question. Your question was answered in your original thread:

https://www.physicsforums.com/showthread.php?t=237561

What you are writing as 1n is actually LN, or the natural log. It is a button on your scientific calculator.
 
it still does not work!
 
bryanehli said:
it still does not work!

Yes it does.

t=(7.5ms) * LN(20v/14.57v) = 2.38ms.

Divide 20/14.57, take the natural log, then multiply by 7.5. I get 2.375something.
 
Thank You!
 

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