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Who or what is Q





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From:  RWB355-at-aol-dot-com [SMTP:RWB355-at-aol-dot-com]
Sent:  Saturday, August 22, 1998 12:41 PM
To:  fwd
Subject:  Who or what is Q

Hi all,

There has been a lot of talk about "Q". Let me see if I can shed some light on
 who or what Q is. 
NO Q isnīt that dude from Star Trek.
Q is a ratio factor that describes the behavior of a circuit. Without running
 a lot of math:

       w(omega) * L
Q=   ------------------ Lets simplify this as w=2* pi*F
            R. 
          2*pi*f*L
=     ------------------
             R

So this means Q is the ratio of inductive reactance to (ohmical) resistance.
 The higer your Q is (Read: high inductive part, low resistance part) the
 "sharper" your resonance curve is (if you plot it). A small Q (e.g.=1) would
 give you a lazy curve like an upside down "U". A high Q (e.g. 1000) on the
 other hand would give you a fast rise / fast drop curve with a real needle
 point as the peak value. The "cut-off", if you will, is much harder. Taking
 this and the transformer laws into account you can now  see why a high Q coil
 will be able to produce a longer and fatter spark. This also shows why you
 canīt (like I first did, growl!!) just go to wire length calculations for your
 secondary. A small coil (high h/d ratio) will have a different inductance than
 a big coil (low h/d ratio) wound with the same length of wire. The big coil
 (using thicker wire) has a better Q, so it will perform better. Of course you
 need to adjust the input power for the bigger coil. The bigger coil will need
 more juice. But if you connect your big ps to the smaller coil you will get
 less output bang for your money. What I find very intersting is that the
 optimal h/d ratio turns out to be Pi (3.14159 etc), but it does make sense if
 you look at several ac equations.

coiler greetings,
Reinhard