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*To*: tesla-at-pupman-dot-com*Subject*: Re: Mot DC Ps*From*: "Tesla list" <tesla-at-pupman-dot-com>*Date*: Sat, 17 Feb 2001 19:57:52 -0700*Resent-Date*: Sat, 17 Feb 2001 20:11:59 -0700*Resent-From*: tesla-at-pupman-dot-com*Resent-Message-ID*: <kfzJIC.A.7Q.81zj6-at-poodle>*Resent-Sender*: tesla-request-at-pupman-dot-com

Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <Mddeming-at-aol-dot-com> In a message dated 2/17/01 4:15:15 PM Eastern Standard Time, tesla-at-pupman-dot-com writes: > > I have a question too when you discharge a cap though a resistance for a > certain value of R you have an oscillating circuit (because of parasitic > inductance ), if you increase the value of R to a certain point the cap > will just discharge whit out oscillation how do you calculate this > value. > > Tx > Luc Benard Hi Luc The critical point is at R=2*sqrt(L/C). If R is greater than this value, no oscillation takes place. The frequency equation f=1/((2pi*sqrt(LC) is actually a simplifications of: F=sqrt(1/LC-(R/2L)^2)/2pi This follows from the circuit current as a function of time being: I(t)=Vo/Lw * exp(-at) * Sin(wt), where a=R/2L and w=sqrt((1/LC)-(R/2L)^2) and Vo is the initial voltage on the capacitor. If you need a complete derivation of this, write me on or off list. Matt D.

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