Series-Parallel RLC circuits and Applications
Impedance can be resistance, reactance, or combination of both A. True B. False
True
above resonant frequency, ____ dominates
XC
Below resonant frequency, ____ dominates
XL
parallel resonance is when
XL = XC
At a low frequency ____ is high, ____ is low
Xc, Xl
at a high frequency ____ is high, ____ is low
Xl, Xc
1/Z = 1/R + 1/XL+ 1/XC can be written as
Z = 1 /(1/R + 1/XL + 1/XC)
A tuned amplifier is a circuit that
amplifies signals within a specified band
The range of frequencies for which current is equal to or greater than 70.7% of its resonant value is known as
bandwidth
when XL < XC, the circuit is predominately
capactive
Resonant circuits are used in a variety of applications, most commonly in
communication
phase angle ____ as the frequency approaches resonant value
decrease
When the same voltage is applied to both circuits, same total currents in both circuits, and phase angle same, it means they are
equivalent
the center frequency (fr) can be found by
f2 + f1 / 2
Bandwidth in formula is
f2 - f1
Audio crossover networks are ____ networks separating audio signals into different frequency bands for the speaker
filter
the formula for bandwidth with Q is
fr / Q
Stored energy is transferred back and forth in a LC circuit on alternate
half-cycles
The upper (f2) and lower (f1) frequencies are sometimes called
half-power frequencies
In ac circuits, the total opposition to current is referred as
impedance
A RLC circuit contains resistance, ____, and capacitance
inductance
when XL > XC, the circuit is predominately
inductive
in an ideal tank circuit the impedance is
infinite
inductive reactance (XL) causes current to ___ the applied voltage
lag
In parallel at high frequencies, XL becomes ____ than XC
larger
capacitive reactance (XC) causes current to ___ the voltage
lead
In parallel RLC circuit at low frequencies, the inductive reactance is ____ than capactive reactance
less
The total current will always be ____ than the individual currents with C and L
less
The voltage across combined L and C is always ____ than the individual voltages across either
less
At series RLC resonant frequency, the current is
maximum
The impedance is ____ at resonant frequency
maximum
The ____ the bandwidth, the greater the selectivity
narrower
Inductive reactance and capacitive reactance have ___ effects on circuit phase angle
opposite
Current is ____ in a parallel RLC circuit between the capactive branch and inductive branch by 180 degrees
out of phase
The resonant circuit is in _____ when used with an amplifier in a tuned amplifier
parallel
if Xl = Xc the two reactances cancel and circuit is purely
resistive
Impedance magnitude is minimum at
resonance
Xl = Xc the circuit is resistive and in
resonance
The frequency at which resonance occurs is called
resonant frequency
How well a resonant circuit responds to a certain frequency and discriminates others is also known as
selectivity
____ of the slope is also a factor that influences selectivity
steepness
A tank circuit can
store energy in magnetic field of the coil and electric field of the capacitor
A parallel resonant LC circuit is usually called
tank circuit
What is used to allow tuning over the range of input frequencies so that a desired frequency is selected
variable capacitor
At series resonant frequency, the voltages across both L and C is
zero
when XL and XC are equal, the resistance is
zero
magnitude of the total reactance in a series RLC circuit is
| XL - XC |
total current can be expressed as a formula as
√(I² + (Ic - IL)² )
total impedance (Z) for series RLC circuit in polar form is
√R² + (XL - XC)² < tan⁻¹(Xtot / R)
The tank circuit is loaded to reduce its
Q
a higher value of ____ results in narrower bandwidth and a lower value of ____ results in wider bandwidth
Q
total impedance (Z) for series RLC circuit in rectangular form is
R + jXL - jXC
Quality factor (Q) is, where ____ equals winding resistance and ____ equals inductive reactance
Rw, XL
Power at f1 or f2 is
0.5P(max)
bandwidth range of series resonant circuit
0.707 * I(max)
bandwidth range of parallel resonant circuit
0.707 * Z(max)
Phase angle at resonance in parallel is
0°
resonant frequency for parallel is
1/ (2π√LC)
the formula for finding resonant frequency
1/(2π√LC)
Conductance (G) is equal to
1/R
Capacitive susceptance (Bc) is equal to
1/XC
Inductive susceptance (Bl) is equal to
1/XL
Admittance (Y) is equal to
1/Z
in a parallel RLC circuit, the total impedance is the reciprocal
1/Z = 1/R + 1/XL+ 1/XC
the parallel resonant frequency of the circuit is about the same as series resonant frequency as long as Q ≥
10
series RLC circuit, the capacitor voltage and inductor voltage are always ____ out of phase
180°
As the frequency goes higher after reaching resonance then the phase angle approaches
90°
at Resonance max Power is
I²R
