Maybe it is time to change the thread.
Passive Resonance is a frequency selective means of storing oscillating
energy. It occurs when energy oscillates back and forth between two
complementary energy storage mechanisms. In the case of the pendulum you
have kinetic and potential energy. In a circuit the storage mechanisms
are the inductance and capacitance. The inductance is the kinetic energy
storage mechanism and the capacitance is the potential storage
mechanism. When there is a balance between these Xc=Xl the circuit is at
resonance. That is because all the energy from one goes to the other and
back except for the bit that is lost in the resistance. A pure resistance
alone is not resonant. That is the flaw in defining resonance as when Xc=Xl
alone. In a resistor zero does equal zero at all frequencies.
Another property of resonance is that besides selectivity the energy
stored in the system is greater than that passing to or from it when at
equilibrium. And the Q is the amount of energy stored divided by the amount
of energy going into the resonant system during each cycle. We usually see
the other definitions regarding reactance and resistance and bandwidth and
resonant frequency. All three produce the same unit-less value.
I use the term passive because some of the properties of passive
resonance (not all) can be accomplished by active filters and by digital
methods. Even though a "flywheel" may store oscillating energy it is not
frequency selective, thus not resonant. We often use the term "Flywheel
Effect" but "Pendulum Effect" may be more accurate.
73
Bill wa4lav
At 10:45 PM 6/4/2006 -0400, Bill Coleman wrote:
>On Jun 4, 2006, at 8:23 AM, R L Measures wrote:
>
> > My dummy load is non-resonant, so that's a problem?
>
>Dummy loads are resonant by definition, since they provide a purely
>resistive impedance. (ie X = 0 is the definition of resonance)
>
>
>
>Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr@arrl.net
>Quote: "Not within a thousand years will man ever fly!"
> -- Wilbur Wright, 1901
>
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