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Math Help - Reversing an algebra question

  1. #1
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    Reversing an algebra question

    Hi all,
    Please be kind to me :-)

    I have this equation,



    where f = Frequency
    L = Inductance
    C = Capacitance

    Now the problem is I know what f & C is. F = 60kHZ and C = 840pF
    Yes this is for an electronics project, I can not work out what L should be, and I have forgotten everything I was learnt when I was at school, many many moons ago !

    Please could someone remind me how to do it

    Thanks in advance

    Chris Yard
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  2. #2
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    Quote Originally Posted by ChrisYard View Post
    Hi all,
    Please be kind to me :-)

    I have this equation,



    where f = Frequency
    L = Inductance
    C = Capacitance

    Now the problem is I know what f & C is. F = 60kHZ and C = 840pF
    Yes this is for an electronics project, I can not work out what L should be, and I have forgotten everything I was learnt when I was at school, many many moons ago !

    Please could someone remind me how to do it

    Thanks in advance

    Chris Yard
    f^2 = \frac{1}{4 \pi^2 LC} \Rightarrow \frac{1}{f^2} = 4 \pi^2 LC \Rightarrow \frac{1}{4 \pi^2 C f^2} = L.
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  3. #3
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    Quote Originally Posted by mr fantastic View Post
    f^2 = \frac{1}{4 \pi^2 LC} \Rightarrow \frac{1}{f^2} = 4 \pi^2 LC \Rightarrow \frac{1}{4 \pi^2 C f^2} = L.
    Thanks mr fantastic, now for some one that is looking through mud !!! sorry for being a pain can I have a step by step ????
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  4. #4
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    Quote Originally Posted by ChrisYard View Post
    Thanks mr fantastic, now for some one that is looking through mud !!! sorry for being a pain can I have a step by step ????
    I have given the algebra step-by-step! Now plug in the numbers and press buttons on a calculator.
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  5. #5
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    Sorry Mr fantastic,

    <br />
f^2 = \frac{1}{4 \pi^2 LC} \Rightarrow \frac{1}{f^2} = 4 \pi^2 LC \Rightarrow \frac{1}{4 \pi^2 C f^2} = L.<br />

    So

    <br />
\frac{1}{25.13274122871835 * 840 * 60000^2} = 0.0000000000000131577.<br />

    ????
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  6. #6
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    Quote Originally Posted by ChrisYard View Post
    Sorry Mr fantastic,

    <br />
f^2 = \frac{1}{4 \pi^2 LC} \Rightarrow \frac{1}{f^2} = 4 \pi^2 LC \Rightarrow \frac{1}{4 \pi^2 C f^2} = L.<br />

    So

    <br />
\frac{1}{25.13274122871835 * 840 * 60000^2} = 0.0000000000000131577.<br />

    ????
    Do you understand what the p in 840 pF means?
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  7. #7
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    Opps sorry, I think I am going to bed and try again tomorrow !!!

    pico = 0.000000000001

    <br />
\frac{1}{25.13274122871835 * 0.00000000000840 * 60000^2} = 1.31576507185760011454<br />

    so that would mean L = 1.315uH
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