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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