Q.1 What is the frequency at which a series RLC circuit resonates?
When the inductive reactance equals the capacitive reactance
When the resistance equals the inductive reactance
When the resistance equals the capacitive reactance
When the inductive reactance is zero
Explanation - In a series RLC circuit, resonance occurs when the inductive reactance (XL = 2πfL) equals the capacitive reactance (XC = 1/(2πfC)), causing the net reactance to be zero.
Correct answer is: When the inductive reactance equals the capacitive reactance
Q.2 Which of the following best describes the Q factor of a resonant circuit?
Ratio of the resonant frequency to bandwidth
Ratio of the bandwidth to resonant frequency
Sum of inductance and capacitance
Difference between inductive and capacitive reactance
Explanation - Quality factor Q = f0 / BW, where f0 is the resonant frequency and BW is the bandwidth over which power drops to half its peak value.
Correct answer is: Ratio of the resonant frequency to bandwidth
Q.3 In a parallel resonant circuit, the current drawn from the source is:
Maximum at resonance
Minimum at resonance
Zero at resonance
Independent of resonance
Explanation - At parallel resonance, the impedance is maximized, causing the current drawn from the source to be minimal.
Correct answer is: Minimum at resonance
Q.4 Which component dominates the energy storage at resonance in an LC circuit?
Resistor
Inductor
Capacitor
Both inductor and capacitor equally
Explanation - At resonance, energy oscillates back and forth between the magnetic field of the inductor and the electric field of the capacitor with equal magnitudes.
Correct answer is: Both inductor and capacitor equally
Q.5 The bandwidth of a resonant circuit is:
f_high - f_low
f_high + f_low
f_high / f_low
f_low / f_high
Explanation - Bandwidth BW is defined as the difference between the upper and lower cutoff frequencies where the power falls to half its peak value.
Correct answer is: f_high - f_low
Q.6 Which of the following frequencies is the resonant frequency of a 10 µH inductor with a 1 µF capacitor?
159 kHz
159 Hz
159 MHz
1.59 MHz
Explanation - f0 = 1/(2π√(LC)) = 1/(2π√(10e-6×1e-6)) ≈ 159,000 Hz = 159 kHz.
Correct answer is: 159 kHz
Q.7 What happens to the resonant frequency if the capacitance in a series LC circuit is increased while keeping inductance constant?
Increases
Decreases
Remains unchanged
First increases then decreases
Explanation - f0 = 1/(2π√(LC)); increasing C lowers the frequency because the denominator increases.
Correct answer is: Decreases
Q.8 Which statement correctly describes the phase relationship at resonance in a series RLC circuit?
Current leads voltage by 90°
Current lags voltage by 90°
Current and voltage are in phase
Current and voltage are 180° out of phase
Explanation - At resonance, inductive and capacitive reactances cancel, leaving only resistance, so current and voltage share the same phase.
Correct answer is: Current and voltage are in phase
Q.9 In a parallel RLC circuit, the current through the inductor and capacitor at resonance:
Is zero
Is maximum and in phase
Is maximum and opposite phase
Is equal to the source current
Explanation - The inductor and capacitor currents are equal in magnitude and opposite in phase, canceling each other, so the net reactive current is zero.
Correct answer is: Is maximum and opposite phase
Q.10 The term 'bandwidth' in an RLC circuit refers to:
The range of frequencies over which the impedance is highest
The range of frequencies over which the impedance is lowest
The range of frequencies over which the current is maximum
The range of frequencies over which the power is half its maximum
Explanation - Bandwidth is the difference between the frequencies at which the power falls to half its maximum (the -3 dB points).
Correct answer is: The range of frequencies over which the power is half its maximum
Q.11 Which component is primarily responsible for determining the quality factor Q in a resonant circuit?
Capacitance
Inductance
Resistance
Supply voltage
Explanation - Q = ω0L/R (series) or Q = R/(ω0L) (parallel); thus resistance largely influences Q.
Correct answer is: Resistance
Q.12 A 100 µH inductor and a 100 nF capacitor are connected in series. What is the approximate resonant frequency?
159 kHz
50.5 kHz
159 Hz
5 kHz
Explanation - f0 = 1/(2π√(100e-6×100e-9)) ≈ 159 kHz.
Correct answer is: 159 kHz
Q.13 If a series RLC circuit has Q = 10 and resonant frequency f0 = 1 kHz, what is its bandwidth?
100 Hz
10 Hz
1 kHz
10 kHz
Explanation - BW = f0/Q = 1000 Hz / 10 = 100 Hz.
Correct answer is: 100 Hz
Q.14 Which of these is a consequence of a high Q factor in a resonant circuit?
Broad bandwidth
Sharp frequency selectivity
High power consumption
Low resonance frequency
Explanation - High Q means narrow bandwidth, leading to sharp selectivity around the resonant frequency.
Correct answer is: Sharp frequency selectivity
Q.15 In a parallel RLC circuit, increasing the resistance R causes which of the following changes?
Increases Q factor
Decreases Q factor
No effect on Q factor
Increases bandwidth
Explanation - For parallel circuits Q = R/(ω0L), so increasing R increases Q, but in practice increasing R tends to broaden the resonance, thus reducing Q (depending on definition).
Correct answer is: Decreases Q factor
Q.16 What is the resonant frequency of a circuit containing a 10 kΩ resistor, 1 µH inductor, and 1 nF capacitor in series?
159 kHz
159 MHz
159 Hz
1.59 MHz
Explanation - f0 ≈ 1/(2π√(1µH×1nF)) ≈ 159 MHz; resistance does not affect f0.
Correct answer is: 159 MHz
Q.17 Which of the following best defines 'bandwidth' in the context of resonant filters?
The frequency difference between the peaks of the transfer function
The frequency at which the output voltage is maximum
The total range of frequencies the filter can pass without attenuation
The difference between the upper and lower cutoff frequencies where the output is half its maximum
Explanation - Bandwidth is defined by the -3 dB points of a filter’s frequency response.
Correct answer is: The difference between the upper and lower cutoff frequencies where the output is half its maximum
Q.18 Which component’s impedance is purely reactive at DC?
Resistor
Inductor
Capacitor
All of the above
Explanation - At DC, a capacitor behaves as an open circuit (infinite impedance) and thus has purely reactive impedance.
Correct answer is: Capacitor
Q.19 The quality factor Q of a tank circuit is defined as:
Resonant frequency divided by bandwidth
Bandwidth divided by resonant frequency
Resonant frequency multiplied by bandwidth
Bandwidth multiplied by resonant frequency
Explanation - Q = f0 / BW, where f0 is resonant frequency and BW is the bandwidth.
Correct answer is: Resonant frequency divided by bandwidth
Q.20 When a parallel RLC circuit is at resonance, the total current drawn from the source is:
Maximum
Minimum
Zero
Indeterminate
Explanation - At resonance, the inductor and capacitor currents cancel, leaving only the resistive current, which is minimal.
Correct answer is: Minimum
Q.21 Which of the following is a characteristic of a high-Q resonant circuit?
Broad frequency response
Rapid energy loss
Narrow bandwidth
Low resonant frequency
Explanation - High Q indicates low energy loss and a narrow bandwidth around the resonant frequency.
Correct answer is: Narrow bandwidth
Q.22 The resonant frequency of a series RLC circuit can be calculated using the formula:
f = 1/(2πR√(LC))
f = 1/(2π√(LC))
f = R/(2πL)
f = √(L/C) / (2π)
Explanation - Resonant frequency depends only on L and C; resistance does not affect the frequency.
Correct answer is: f = 1/(2π√(LC))
Q.23 In a series resonant circuit, if the resistance increases, the resonant frequency:
Increases
Decreases
Remains unchanged
Becomes zero
Explanation - The resonant frequency is determined solely by L and C, not R.
Correct answer is: Remains unchanged
Q.24 Which frequency is called the 'half-power point' in a resonant circuit?
f0 - BW/2
f0 + BW/2
Both f0 - BW/2 and f0 + BW/2
f0
Explanation - At these frequencies, the power is half its maximum (−3 dB points).
Correct answer is: Both f0 - BW/2 and f0 + BW/2
Q.25 A 5 kΩ resistor, a 100 µH inductor, and a 10 µF capacitor are connected in series. What is the resonant frequency?
79.6 Hz
159.2 Hz
1.59 Hz
159.2 kHz
Explanation - f0 = 1/(2π√(100e-6×10e-6)) ≈ 159 Hz.
Correct answer is: 159.2 Hz
Q.26 What is the effect of a parallel RLC circuit resonating on the voltage across the capacitor?
It becomes zero
It becomes very large
It equals the source voltage
It is independent of resonance
Explanation - At parallel resonance, the impedance is high, causing the voltage across the reactive components to be large.
Correct answer is: It becomes very large
Q.27 Which of the following correctly represents the inductive reactance?
XL = 2πfL
XL = 1/(2πfL)
XL = 2πfC
XL = 1/(2πfC)
Explanation - Inductive reactance increases linearly with frequency and inductance.
Correct answer is: XL = 2πfL
Q.28 If the capacitance in a resonant circuit is doubled, the resonant frequency will:
Double
Halve
Increase by sqrt(2)
Decrease by sqrt(2)
Explanation - f0 ∝ 1/√C; doubling C reduces f0 by √2.
Correct answer is: Decrease by sqrt(2)
Q.29 In a series RLC circuit, the impedance is at its minimum at:
Zero frequency
Resonant frequency
Infinite frequency
Half of the resonant frequency
Explanation - At resonance, the reactive parts cancel, leaving only resistance, thus minimizing impedance.
Correct answer is: Resonant frequency
Q.30 Which parameter is most directly related to energy loss per cycle in a resonant circuit?
Inductance
Capacitance
Resistance
Frequency
Explanation - Resistance dissipates energy as heat, causing loss per cycle.
Correct answer is: Resistance
Q.31 The term 'resonant bandwidth' refers to:
The range of frequencies where the circuit is resonant
The frequency range over which the power is at maximum
The range of frequencies where impedance is minimum
The difference between the resonant frequency and the cutoff frequency
Explanation - Bandwidth is the width of the resonance peak, typically defined by the -3 dB points.
Correct answer is: The range of frequencies where the circuit is resonant
Q.32 In a resonant tank circuit, the energy stored in the inductor equals the energy stored in the capacitor at any instant during oscillation. This is an example of:
Steady state
Transitional state
Resonant condition
Damped oscillation
Explanation - At resonance, energy continuously swaps between magnetic and electric fields without loss.
Correct answer is: Resonant condition
Q.33 Which of the following is true for a parallel LC circuit at resonance?
Net current from source is maximum
Net current from source is minimum
Voltage across inductor is zero
Voltage across capacitor is zero
Explanation - The inductor and capacitor currents cancel, leaving minimal net current.
Correct answer is: Net current from source is minimum
Q.34 Resonance can be described as:
When the input voltage is zero
When the reactive impedances cancel each other out
When the resistor dominates the impedance
When the circuit has infinite impedance
Explanation - Resonance occurs when inductive reactance equals capacitive reactance, making the net reactance zero.
Correct answer is: When the reactive impedances cancel each other out
Q.35 Which circuit component is responsible for storing magnetic energy?
Capacitor
Resistor
Inductor
Diode
Explanation - Inductors store energy in their magnetic fields.
Correct answer is: Inductor
Q.36 Which of the following is a real-world application of resonance?
Radio tuning
Battery charging
Light bulb illumination
Motor starting
Explanation - Resonant circuits are used to select specific frequencies in radios and televisions.
Correct answer is: Radio tuning
Q.37 A series RLC circuit has a resonant frequency of 1 kHz and Q = 20. What is its bandwidth?
50 Hz
20 Hz
200 Hz
2000 Hz
Explanation - BW = f0/Q = 1000 Hz / 20 = 50 Hz.
Correct answer is: 50 Hz
Q.38 In a resonant tank circuit, the impedance is:
Maximum at resonance
Minimum at resonance
Zero at resonance
Equal to resistance at all frequencies
Explanation - For parallel resonance, the impedance peaks, causing a large voltage across reactive components.
Correct answer is: Maximum at resonance
Q.39 When the frequency of a series RLC circuit is below the resonant frequency, the circuit is:
Capacitive
Inductive
Resistive
Neutral
Explanation - Below resonance, capacitive reactance dominates, making the circuit behave as a capacitor.
Correct answer is: Capacitive
Q.40 When the frequency of a series RLC circuit is above the resonant frequency, the circuit is:
Capacitive
Inductive
Resistive
Neutral
Explanation - Above resonance, inductive reactance dominates, making the circuit behave as an inductor.
Correct answer is: Inductive
Q.41 A resonant circuit with a very high Q factor will:
Have a very broad bandwidth
Respond quickly to frequency changes
Have a narrow bandwidth
Produce high voltage noise
Explanation - High Q implies low damping, leading to a sharp, narrow resonance peak.
Correct answer is: Have a narrow bandwidth
Q.42 Which component in a resonant circuit does not store energy?
Resistor
Inductor
Capacitor
All of them store energy
Explanation - Resistors dissipate energy as heat rather than store it.
Correct answer is: Resistor
Q.43 What is the formula for the resonant frequency of a parallel RLC circuit?
f0 = 1/(2π√(LC))
f0 = 1/(2πRC)
f0 = 1/(2π√(RC))
f0 = 1/(2πRL)
Explanation - Resonance depends only on L and C regardless of the connection type.
Correct answer is: f0 = 1/(2π√(LC))
Q.44 Which of the following best describes a band‑pass filter?
Passes all frequencies
Passes only one frequency
Passes a band of frequencies around a center frequency
Blocks all frequencies
Explanation - A band‑pass filter allows a specific range of frequencies to pass while attenuating others.
Correct answer is: Passes a band of frequencies around a center frequency
Q.45 The phase shift in a series RLC circuit at resonance is:
0°
90°
-90°
180°
Explanation - At resonance the reactive parts cancel, so voltage and current are in phase.
Correct answer is: 0°
Q.46 In a parallel RLC circuit, what is the relationship between impedance and frequency at resonance?
Impedance is minimum
Impedance is maximum
Impedance is zero
Impedance is equal to resistance
Explanation - Parallel resonance creates a high impedance point.
Correct answer is: Impedance is maximum
Q.47 Which of the following best explains why a resonant circuit can oscillate without an external source?
Energy continuously exchanges between magnetic and electric fields
Resistors amplify energy
Capacitors charge indefinitely
Inductors create magnetic fields that never decay
Explanation - Stored energy in L and C keeps the circuit oscillating as long as loss is minimal.
Correct answer is: Energy continuously exchanges between magnetic and electric fields
Q.48 In a series RLC circuit, increasing the resistance R causes:
An increase in resonant frequency
A decrease in resonant frequency
A decrease in bandwidth
An increase in bandwidth
Explanation - Higher R increases damping, broadening the resonance peak (greater bandwidth).
Correct answer is: An increase in bandwidth
Q.49 The resonant frequency of a 5 µH inductor and a 200 pF capacitor is:
25.3 MHz
25.3 kHz
253 Hz
253 MHz
Explanation - f0 = 1/(2π√(5e-6×200e-12)) ≈ 25.3 MHz.
Correct answer is: 25.3 MHz
Q.50 In a series RLC circuit, the total impedance is minimum at resonance because:
Inductive and capacitive reactances sum to zero
The resistance is zero
Both reactances are infinite
The supply voltage is zero
Explanation - At resonance, XL = XC, so net reactance cancels, leaving only R.
Correct answer is: Inductive and capacitive reactances sum to zero
Q.51 What is the effect on the resonant frequency if the inductance is increased while capacitance remains constant?
Frequency increases
Frequency decreases
Frequency remains unchanged
Frequency becomes zero
Explanation - f0 ∝ 1/√L; increasing L lowers the resonant frequency.
Correct answer is: Frequency decreases
Q.52 Which of the following is a typical use for a band‑stop filter?
To pass all frequencies
To block a narrow band of frequencies
To amplify a specific frequency
To provide a DC offset
Explanation - Band‑stop (notch) filters reject signals within a narrow frequency band.
Correct answer is: To block a narrow band of frequencies
Q.53 If an RLC circuit is operating at resonance, the power factor is:
0
0.5
0.707
1
Explanation - At resonance, voltage and current are in phase, giving a power factor of unity.
Correct answer is: 1
Q.54 In a parallel RLC circuit, the magnitude of impedance at resonance is:
Zero
Equal to R
Maximum possible
Minimum possible
Explanation - Impedance peaks at resonance, causing minimal current draw from the source.
Correct answer is: Maximum possible
Q.55 Which component will be primarily responsible for a high resonant frequency in an LC circuit?
Large capacitance
Small inductance
High resistance
Large inductance
Explanation - A smaller L yields a higher f0 for a given C.
Correct answer is: Small inductance
Q.56 The total energy stored in an L‑C resonant circuit at any instant is:
E = 0.5 L I² + 0.5 C V²
E = L I + C V
E = L I²
E = C V²
Explanation - Energy stored in L is 0.5LI²; in C is 0.5CV²; total is the sum.
Correct answer is: E = 0.5 L I² + 0.5 C V²
Q.57 In a parallel resonant circuit, the resonant current is:
Zero
Maximum
Equal to source current
Independent of resonance
Explanation - At resonance, the reactive currents cancel, leaving zero net current.
Correct answer is: Zero
Q.58 Which of the following is NOT a characteristic of a series resonant circuit?
Impedance is minimum at resonance
Voltage across L and C are equal in magnitude
The circuit has a high Q factor
The circuit blocks all frequencies
Explanation - A series resonant circuit allows the resonant frequency to pass, not block all frequencies.
Correct answer is: The circuit blocks all frequencies
Q.59 The resonant frequency of a 2 µH inductor and a 50 pF capacitor is approximately:
22.4 MHz
4.44 MHz
224 kHz
44.4 kHz
Explanation - f0 = 1/(2π√(2e-6×50e-12)) ≈ 22.4 MHz.
Correct answer is: 22.4 MHz
Q.60 Which parameter of an RLC circuit determines how quickly the circuit settles after a disturbance?
Capacitance
Inductance
Resistance
Frequency
Explanation - Higher R causes faster damping, leading to quicker settling.
Correct answer is: Resistance
Q.61 In a resonant circuit, the term 'half‑power point' refers to:
The frequency where impedance is half its maximum
The frequency where power is half its maximum
The frequency where voltage is half its maximum
The frequency where current is half its maximum
Explanation - Half‑power points are at -3 dB, where the power drops to 50% of its peak.
Correct answer is: The frequency where power is half its maximum
Q.62 A series resonant circuit with R = 10 Ω, L = 100 µH, C = 100 nF has a resonant frequency of:
50.3 kHz
159.2 kHz
5.03 kHz
1.59 kHz
Explanation - f0 = 1/(2π√(100e-6×100e-9)) ≈ 159.2 kHz.
Correct answer is: 159.2 kHz
Q.63 Which of the following best describes a 'notch filter' in signal processing?
It allows all frequencies to pass
It blocks a narrow band of frequencies
It blocks high frequencies
It amplifies a specific frequency
Explanation - A notch filter rejects a small range of frequencies while allowing others.
Correct answer is: It blocks a narrow band of frequencies
Q.64 In a parallel RLC circuit, what happens to the impedance when the resistance is very high?
Impedance decreases
Impedance remains the same
Impedance increases
Impedance becomes zero
Explanation - High resistance raises the overall impedance of the parallel network.
Correct answer is: Impedance increases
Q.65 Which component in an LC resonant circuit has zero impedance at the resonant frequency?
Resistor
Inductor
Capacitor
None of them
Explanation - At resonance, the inductive reactance equals the capacitive reactance, but neither is zero.
Correct answer is: None of them
Q.66 The resonant frequency of a 10 kΩ resistor, 10 mH inductor, and 1 µF capacitor in series is:
159 Hz
15.9 Hz
1.59 kHz
159 kHz
Explanation - f0 = 1/(2π√(10e-3×1e-6)) ≈ 159 Hz; resistance does not affect f0.
Correct answer is: 159 Hz
Q.67 What is the primary difference between series and parallel resonant circuits?
Series has maximum impedance at resonance; parallel has minimum
Series has minimum impedance at resonance; parallel has maximum
Series uses inductors; parallel uses capacitors
Series uses resistors; parallel does not
Explanation - Resonant behavior is inverted between the two topologies.
Correct answer is: Series has minimum impedance at resonance; parallel has maximum
Q.68 Which of the following is a correct expression for the resonant bandwidth of a series RLC circuit?
BW = R / (2πL)
BW = 2πL / R
BW = R / (2πC)
BW = 2πC / R
Explanation - Bandwidth for series RLC is given by R/(2πL).
Correct answer is: BW = R / (2πL)
Q.69 In a resonant circuit, which of the following will increase the Q factor if added in series?
Additional inductance
Additional capacitance
Additional resistance
Additional voltage source
Explanation - Increasing L increases Q = ω0L/R for series circuits.
Correct answer is: Additional inductance
Q.70 At resonance in a series RLC circuit, the voltage across the resistor is:
Zero
Maximum
Same as source voltage
Half of source voltage
Explanation - Resonance amplifies the current, leading to higher voltage drop across R.
Correct answer is: Maximum
Q.71 Which of the following best describes a resonant circuit's energy loss over time?
No loss; energy remains constant
Loss proportional to inductance
Loss proportional to capacitance
Loss proportional to resistance
Explanation - Resistance dissipates energy as heat, causing gradual loss.
Correct answer is: Loss proportional to resistance
Q.72 What is the resonant frequency of a 5 µH inductor and a 200 pF capacitor?
3.55 MHz
35.5 kHz
355 Hz
355 MHz
Explanation - f0 = 1/(2π√(5e-6×200e-12)) ≈ 3.55 MHz.
Correct answer is: 3.55 MHz
Q.73 In a series resonant circuit, the current amplitude is:
Maximum at resonance
Minimum at resonance
Zero at resonance
Independent of resonance
Explanation - Low impedance at resonance allows maximum current for a given source voltage.
Correct answer is: Maximum at resonance
Q.74 Which parameter of a resonant circuit determines the sharpness of the resonance peak?
Capacitance
Inductance
Resistance
Frequency
Explanation - Lower resistance leads to a sharper (higher Q) resonance peak.
Correct answer is: Resistance
Q.75 What happens to the resonant frequency of a parallel RLC circuit if the resistance is decreased?
Frequency increases
Frequency decreases
Frequency remains unchanged
Frequency becomes zero
Explanation - Resonant frequency depends only on L and C, not R.
Correct answer is: Frequency remains unchanged
Q.76 In a resonant LC circuit, the time constant τ for the voltage across the capacitor is:
L / R
R / L
1 / (ω0 C)
ω0 C
Explanation - τ = L/R describes the rate of decay of current in a series RLC circuit.
Correct answer is: L / R
Q.77 Which of the following best defines the term 'bandwidth' in a resonant circuit?
Range of frequencies over which impedance is minimal
Range of frequencies over which power is maximum
Difference between the resonant frequency and cutoff frequencies
The resonant frequency itself
Explanation - Bandwidth is the width of the resonance peak, defined by cutoff points.
Correct answer is: Difference between the resonant frequency and cutoff frequencies
Q.78 If you increase both L and C in a resonant circuit by the same factor, the resonant frequency:
Increases
Decreases
Remains the same
Becomes zero
Explanation - f0 = 1/(2π√(LC)); scaling both L and C by same factor keeps product unchanged.
Correct answer is: Remains the same
Q.79 The resonant frequency of an RLC circuit with L = 2 mH and C = 5 µF is approximately:
4 kHz
40 Hz
400 Hz
4 Hz
Explanation - f0 = 1/(2π√(2e-3×5e-6)) ≈ 400 Hz.
Correct answer is: 400 Hz
Q.80 What is the impedance of a parallel RLC circuit at resonance if R = 10 kΩ?
10 kΩ
Infinite
Zero
Half of 10 kΩ
Explanation - At parallel resonance, impedance theoretically tends to infinity.
Correct answer is: Infinite
Q.81 In a parallel resonant circuit, the current through the resistor at resonance is:
Zero
Maximum
Equal to source current
Independent of resonance
Explanation - Resonance maximizes total impedance, reducing current; the resistor current is the main path, so it is maximum relative to reactive currents.
Correct answer is: Maximum
Q.82 Which of the following best illustrates energy conservation in a resonant tank circuit?
Energy dissipates as heat over time
Energy continuously exchanges between magnetic and electric fields
Energy is stored only in the capacitor
Energy is stored only in the inductor
Explanation - In an ideal tank, energy alternates between L and C without loss.
Correct answer is: Energy continuously exchanges between magnetic and electric fields
Q.83 Which parameter is directly proportional to the bandwidth of a parallel resonant circuit?
Capacitance
Inductance
Resistance
Resonant frequency
Explanation - Bandwidth BW = R/(2πL); thus increasing R increases BW.
Correct answer is: Resistance
Q.84 The quality factor Q of a resonant circuit can also be expressed as:
f0 / (2πR)
R / (ω0 L)
ω0 L / R
L / (ω0 R)
Explanation - For series RLC, Q = ω0L / R; for parallel, Q = R / (ω0L).
Correct answer is: ω0 L / R
Q.85 Which of the following is NOT a typical characteristic of a resonant circuit?
Sharp frequency selectivity
High energy storage
Infinite bandwidth
Energy exchange between L and C
Explanation - Resonant circuits have finite, often narrow bandwidth.
Correct answer is: Infinite bandwidth
Q.86 In a series resonant circuit, the magnitude of the current is:
Maximum at the resonant frequency
Zero at the resonant frequency
Constant across all frequencies
Maximum at the cutoff frequency
Explanation - Resonance provides minimal impedance, allowing maximum current.
Correct answer is: Maximum at the resonant frequency
Q.87 What is the effect on the resonant frequency if both L and C are halved in a resonant circuit?
Frequency increases by √2
Frequency decreases by √2
Frequency remains unchanged
Frequency doubles
Explanation - f0 ∝ 1/√(LC); halving each halves the product, so frequency increases by √2.
Correct answer is: Frequency increases by √2
Q.88 Which of the following best describes the 'Q' of a resonant circuit?
The ratio of the reactive to resistive power
The ratio of resonant frequency to bandwidth
The ratio of stored to dissipated energy per cycle
All of the above
Explanation - All three expressions are equivalent descriptions of the quality factor.
Correct answer is: All of the above
Q.89 What happens to the resonant frequency of a circuit if the inductance is tripled while capacitance is halved?
Frequency increases by √3
Frequency decreases by √3
Frequency remains unchanged
Frequency becomes zero
Explanation - f0 = 1/(2π√(LC)); product LC increases by 3/2, so f0 decreases by √(3/2) ≈ 1.225.
Correct answer is: Frequency decreases by √3
Q.90 Which of the following is a practical example of a resonant circuit?
Battery
Transformer
RF antenna
LED driver
Explanation - RF antennas are tuned to resonate at specific frequencies for efficient radiation.
Correct answer is: RF antenna
Q.91 In a resonant circuit, the power delivered to the load at resonance is:
Zero
Maximum
Equal to half the input power
Independent of resonance
Explanation - Resonance maximizes current and hence power into the load.
Correct answer is: Maximum
Q.92 The resonant frequency of a 1 kΩ resistor, 1 mH inductor, and 1 µF capacitor in series is approximately:
159 Hz
15.9 Hz
1590 Hz
159 kHz
Explanation - f0 = 1/(2π√(1e-3×1e-6)) ≈ 159 Hz.
Correct answer is: 159 Hz
Q.93 Which of the following parameters is inversely proportional to the resonant frequency in a resonant circuit?
Inductance
Capacitance
Resistance
Both Inductance and Capacitance
Explanation - f0 ∝ 1/√(LC), so increasing either L or C lowers f0.
Correct answer is: Both Inductance and Capacitance
Q.94 In a parallel resonant circuit, the resonant impedance is:
Zero
Minimum
Maximum
Same as resistance
Explanation - Parallel resonance maximizes impedance, minimizing current draw.
Correct answer is: Maximum
Q.95 The expression for resonant frequency in an RLC circuit can also be written as:
f0 = 1/(2πRC)
f0 = 1/(2π√(LC))
f0 = √(R/L)
f0 = R/(2πL)
Explanation - The resonant frequency depends only on L and C, not R.
Correct answer is: f0 = 1/(2π√(LC))
Q.96 Which of the following best describes a band‑stop filter?
Passes a narrow band of frequencies
Blocks a narrow band of frequencies
Amplifies a specific frequency
Blocks all frequencies
Explanation - Band‑stop (notch) filters reject signals within a narrow frequency range.
Correct answer is: Blocks a narrow band of frequencies
Q.97 If the resistance in a series RLC circuit is increased, the Q factor:
Increases
Decreases
Remains unchanged
Becomes zero
Explanation - Q = ω0L/R; higher R lowers Q.
Correct answer is: Decreases
Q.98 What is the bandwidth of a parallel RLC circuit with R = 100 Ω, L = 1 mH, and C = 10 nF?
15.9 kHz
159 Hz
159.2 kHz
1.59 kHz
Explanation - BW = R/(2πL) = 100/(2π×1e-3) ≈ 159.2 kHz.
Correct answer is: 159.2 kHz
Q.99 The resonant frequency of a 10 nF capacitor and a 2 mH inductor is:
20 kHz
2 kHz
200 Hz
2000 Hz
Explanation - f0 = 1/(2π√(2e-3×10e-9)) ≈ 20 kHz.
Correct answer is: 20 kHz
Q.100 In a series resonant circuit, the phase shift between voltage and current at resonance is:
0°
90°
-90°
180°
Explanation - Voltage and current are in phase at resonance.
Correct answer is: 0°
Q.101 The energy stored in the capacitor at resonance is equal to:
The energy stored in the inductor
Zero
The sum of energies stored in both
The product of energies stored in both
Explanation - At resonance, energy oscillates between L and C, so they are equal at any instant.
Correct answer is: The energy stored in the inductor
Q.102 Which parameter determines the width of the resonance peak in a resonant circuit?
Inductance
Capacitance
Resistance
Supply voltage
Explanation - Higher resistance increases damping and widens the peak.
Correct answer is: Resistance
Q.103 A resonant tank circuit with L = 10 mH and C = 100 nF has a resonant frequency of:
5.01 kHz
50.1 kHz
501 Hz
5.01 Hz
Explanation - f0 = 1/(2π√(10e-3×100e-9)) ≈ 5.01 kHz.
Correct answer is: 5.01 kHz
Q.104 In a parallel RLC circuit, if the capacitance is doubled, the resonant frequency:
Increases by √2
Decreases by √2
Remains the same
Doubles
Explanation - f0 ∝ 1/√C; doubling C lowers f0 by √2.
Correct answer is: Decreases by √2
Q.105 What is the main advantage of using a resonant filter in a communication system?
To increase signal strength across all frequencies
To reject unwanted frequencies while allowing desired ones
To reduce the need for power supplies
To eliminate noise completely
Explanation - Resonant filters provide selective frequency response.
Correct answer is: To reject unwanted frequencies while allowing desired ones
Q.106 The bandwidth of a series RLC circuit is directly proportional to:
Resistor value R
Inductor value L
Capacitor value C
Resonant frequency f0
Explanation - BW = R/(2πL); increasing R widens bandwidth.
Correct answer is: Resistor value R
Q.107 If the resistance is increased in a parallel RLC circuit, the Q factor:
Increases
Decreases
Remains unchanged
Becomes zero
Explanation - Q = R/(ω0L); higher R raises Q for parallel circuits.
Correct answer is: Increases
Q.108 A resonant circuit with an ideal inductor and capacitor will have:
Infinite bandwidth
Zero bandwidth
Finite bandwidth determined by R
Infinite Q factor
Explanation - With no resistance, energy loss is zero, leading to infinite Q.
Correct answer is: Infinite Q factor
Q.109 Which of the following is NOT part of the standard definition of a resonant circuit?
Inductor
Capacitor
Resistor
Transistor
Explanation - Resonant circuits are built from L, C, and R; transistors are not required.
Correct answer is: Transistor
Q.110 The resonant frequency of a 50 µH inductor and a 100 pF capacitor is approximately:
6.3 MHz
63 kHz
630 Hz
63 MHz
Explanation - f0 = 1/(2π√(50e-6×100e-12)) ≈ 6.3 MHz.
Correct answer is: 6.3 MHz
Q.111 The quality factor Q of an RLC circuit is higher when:
Resistance is high
Resistance is low
Inductance is low
Capacitance is low
Explanation - Lower R reduces energy loss, raising Q.
Correct answer is: Resistance is low
Q.112 Which of the following best describes a narrowband filter?
Passes a wide range of frequencies
Passes a narrow range of frequencies
Blocks all frequencies
Amplifies all frequencies
Explanation - Narrowband filters allow only a small frequency band to pass.
Correct answer is: Passes a narrow range of frequencies
Q.113 The impedance of a parallel RLC circuit at resonance is:
Zero
Minimum
Maximum
Same as source impedance
Explanation - Parallel resonance produces a high impedance point.
Correct answer is: Maximum
Q.114 In a resonant tank circuit, the instantaneous voltage across the capacitor is:
Equal to the source voltage
Zero at resonance
Maximum when current is zero
Constant over time
Explanation - At resonance, energy swings from capacitor to inductor; voltage peaks when current passes through zero.
Correct answer is: Maximum when current is zero
Q.115 Which of the following is a common method to tune a resonant circuit to a desired frequency?
Adjusting the supply voltage
Changing the resistor value
Changing the inductance or capacitance
Changing the ambient temperature
Explanation - Resonant frequency depends on L and C, so altering them tunes the circuit.
Correct answer is: Changing the inductance or capacitance
Q.116 A resonant circuit can be used to:
Select a specific frequency band in a radio
Store electrical energy indefinitely
Convert AC to DC
Eliminate all electrical noise
Explanation - Resonant circuits are integral to radio tuning and frequency selection.
Correct answer is: Select a specific frequency band in a radio
Q.117 The bandwidth of a series RLC circuit is inversely proportional to:
Inductance L
Resistance R
Capacitance C
Frequency f0
Explanation - BW = R/(2πL); increasing L decreases bandwidth.
Correct answer is: Inductance L
Q.118 Which of the following is true about the resonant frequency of a circuit with L = 100 µH and C = 10 nF?
It is independent of L and C
It increases with L and decreases with C
It decreases with L and increases with C
It is determined solely by the resistor
Explanation - f0 ∝ 1/√(LC), so larger L lowers frequency and larger C lowers frequency.
Correct answer is: It decreases with L and increases with C
Q.119 If the inductance in a resonant circuit is increased by a factor of 4, the resonant frequency will:
Decrease by a factor of 2
Increase by a factor of 2
Decrease by a factor of √4
Remain the same
Explanation - f0 ∝ 1/√L; doubling L halves f0, so quadrupling L halves f0 again.
Correct answer is: Decrease by a factor of 2
Q.120 In a series resonant circuit, the magnitude of impedance is minimum at:
Zero frequency
Resonant frequency
Infinite frequency
Half of the resonant frequency
Explanation - Impedance is minimum when reactive parts cancel at resonance.
Correct answer is: Resonant frequency
Q.121 Which of the following best describes a resonant tank circuit?
A circuit that stores energy and oscillates at a particular frequency
A circuit that converts AC to DC
A circuit that provides a stable DC voltage
A circuit that eliminates all inductive reactance
Explanation - An LC tank stores energy between magnetic and electric fields and oscillates at its resonant frequency.
Correct answer is: A circuit that stores energy and oscillates at a particular frequency
Q.122 The resonant frequency of a parallel RLC circuit with L = 1 mH and C = 1 µF is:
159 Hz
1590 Hz
15.9 Hz
159 kHz
Explanation - f0 = 1/(2π√(1e-3×1e-6)) ≈ 159 Hz.
Correct answer is: 159 Hz
Q.123 In a resonant circuit, the total power dissipated in the resistor at resonance is:
Zero
Maximum
Half the input power
Independent of resonance
Explanation - At resonance, current is maximum, leading to maximum power dissipation in the resistor.
Correct answer is: Maximum
Q.124 Which of the following best describes the function of a band‑pass filter in an RF circuit?
It blocks all frequencies below a certain threshold
It allows a specific frequency band to pass while rejecting others
It amplifies all incoming signals
It converts DC to AC
Explanation - Band‑pass filters transmit only signals within a particular frequency band.
Correct answer is: It allows a specific frequency band to pass while rejecting others
Q.125 A resonant circuit has L = 10 mH and C = 1 µF. If R = 50 Ω, the Q factor is:
31.8
63.7
15.9
0.159
Explanation - Q = ω0L/R = (2π×159)×0.01/50 ≈ 31.8.
Correct answer is: 31.8