- #1

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**What does "In" equal?**

In a RL circuir time constant formula what does the "In" indicate? This is probably very simple but it has got me stumped. Such as t=TIn(E/Vl). All help is appreciated!

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- Thread starter bryanehli
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- #1

- 5

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In a RL circuir time constant formula what does the "In" indicate? This is probably very simple but it has got me stumped. Such as t=TIn(E/Vl). All help is appreciated!

- #2

Mentor

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Welcome to the PF, Bryan. I'm not sure what your equation represents. As described at this web page:

http://en.wikipedia.org/wiki/Time_constant

the time constant for an LR circuit is L/R. Could you please review that web page, and then if you still have a question, please post more information about the equation you are asking about.

- #3

Gold Member

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On my calculator, LOG stands for base 10 logarithms and LN stands for natural logarithms.

So your formula might be rewritten to avoid confusion as t=T*LN(E/Vl)

- #4

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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?

- #5

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Its not 'In', the symbol is Ln, or some people write L as 'l', and unfortunately 'l' looks like 'I'

http://en.wikipedia.org/wiki/Natural_logarithm

- #6

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Ln relates to 'e' and hopefully you recognize that. if not... look in a book.

e^(Ln(x)) = x

Ln(e) = 1

- #7

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Another interesting thing about e, aka Euler's Number, is this:

f(x) = e^x

f ' (x) = e^x

f(x) = e^x

f ' (x) = e^x

- #8

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e^(pi*i)= -1

Longer Discussion here:

http://www.math.toronto.edu/mathnet/questionCorner/epii.html

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