Applications of resonance
So far, the phenomenon of resonance
appears to be a useless curiosity, or at most a nuisance to be avoided
(especially if series resonance makes for a short-circuit across our AC
voltage source!). However, this is not the case. Resonance is a very
valuable property of reactive AC circuits, employed in a variety of
applications.
One use for resonance is to establish a
condition of stable frequency in circuits designed to produce AC
signals. Usually, a parallel (tank) circuit is used for this purpose,
with the capacitor and inductor directly connected together, exchanging
energy between each other. Just as a pendulum can be used to stabilize
the frequency of a clock mechanism's oscillations, so can a tank circuit
be used to stabilize the electrical frequency of an AC oscillator
circuit. As was noted before, the frequency set by the tank circuit is
solely dependent upon the values of L and C, and not on the magnitudes
of voltage or current present in the oscillations:
Another use for resonance is in
applications where the effects of greatly increased or decreased
impedance at a particular frequency is desired. A resonant circuit can
be used to "block" (present high impedance toward) a frequency or range
of frequencies, thus acting as a sort of frequency "filter" to strain
certain frequencies out of a mix of others. In fact, these particular
circuits are called filters, and their design constitutes a
discipline of study all by itself:
In essence, this is how analog radio
receiver tuner circuits work to filter, or select, one station frequency
out of the mix of different radio station frequency signals intercepted
by the antenna.
- REVIEW:
- Resonance can be employed to maintain
AC circuit oscillations at a constant frequency, just as a pendulum
can be used to maintain constant oscillation speed in a timekeeping
mechanism.
- Resonance can be exploited for its
impedance properties: either dramatically increasing or decreasing
impedance for certain frequencies. Circuits designed to screen certain
frequencies out of a mix of different frequencies are called
filters.
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