Q.1 What is the definition of resonance in an RLC series circuit?
When the inductive reactance equals the capacitive reactance
When the resistance is zero
When the voltage across the resistor is maximum
When the current is minimum
Explanation - Resonance in a series RLC circuit occurs when the inductive reactance (XL = 2πfL) equals the capacitive reactance (XC = 1/(2πfC)), causing the impedance to be purely resistive and the current to be maximum.
Correct answer is: When the inductive reactance equals the capacitive reactance
Q.2 In a parallel RLC circuit, the resonant frequency is given by which formula?
f0 = 1/(2π√(LC))
f0 = 1/(2πL C)
f0 = √(L/C)
f0 = √(C/L)
Explanation - For both series and parallel RLC circuits, the resonant frequency is f0 = 1/(2π√(LC)). The difference lies in the impedance behavior at resonance.
Correct answer is: f0 = 1/(2π√(LC))
Q.3 What happens to the impedance of a series RLC circuit at resonance?
It becomes equal to the resistance only
It becomes infinite
It becomes zero
It becomes the sum of L and C reactances
Explanation - At resonance, XL = XC, so they cancel each other out, leaving only the resistor R as the total impedance.
Correct answer is: It becomes equal to the resistance only
Q.4 Which component determines the bandwidth of a series RLC circuit?
Inductor
Capacitor
Resistor
All of the above
Explanation - The bandwidth (Δf) of a series RLC circuit is Δf = R/(2πL). Thus, the resistance controls the bandwidth.
Correct answer is: Resistor
Q.5 If a series RLC circuit has a quality factor Q = 50 and resonant frequency f0 = 1 kHz, what is the bandwidth Δf?
20 Hz
10 Hz
5 Hz
2.5 Hz
Explanation - Q = f0 / Δf → Δf = f0 / Q = 1000 / 50 = 20 Hz.
Correct answer is: 20 Hz
Q.6 Which of the following is a characteristic of a parallel RLC circuit at resonance?
Maximum current through the circuit
Minimum current through the circuit
Maximum voltage across the resistor
Minimum voltage across the resistor
Explanation - At resonance in a parallel RLC, the inductive and capacitive currents cancel, leading to minimal total current drawn from the source.
Correct answer is: Minimum current through the circuit
Q.7 Resonance occurs at the same frequency in which of the following?
Both series and parallel RLC circuits with the same L and C
Only in series circuits
Only in parallel circuits
Neither, they have different resonant frequencies
Explanation - The resonant frequency depends only on L and C: f0 = 1/(2π√(LC)).
Correct answer is: Both series and parallel RLC circuits with the same L and C
Q.8 What is the expression for the reactance of a capacitor at angular frequency ω?
XC = 1/(ωC)
XC = ωC
XC = 1/(2πfC)
XC = 2πfC
Explanation - The capacitive reactance is given by XC = 1/(ωC), where ω = 2πf.
Correct answer is: XC = 1/(ωC)
Q.9 In an RLC circuit, which parameter increases the sharpness of the resonance peak?
Increase the resistance
Decrease the resistance
Increase the inductance
Increase the capacitance
Explanation - A lower resistance leads to a higher Q factor, resulting in a sharper resonance peak.
Correct answer is: Decrease the resistance
Q.10 For a series RLC circuit, the resonant frequency f0 is 200 kHz. If the inductance L is 1 µH, what is the required capacitance C?
0.125 µF
0.000125 µF
125 µF
0.00125 µF
Explanation - f0 = 1/(2π√(LC)) → C = 1/( (2πf0)^2 * L ) ≈ 0.000125 µF.
Correct answer is: 0.000125 µF
Q.11 Which of the following statements is true for a parallel RLC circuit at resonance?
The total impedance is zero
The total impedance is infinite
The total impedance is equal to R
The total impedance is equal to L + C
Explanation - At resonance, the inductive and capacitive admittances cancel, leaving the resistor in parallel with an open circuit, making total impedance infinite.
Correct answer is: The total impedance is infinite
Q.12 What is the power dissipated in a series RLC circuit at resonance if the source voltage is 10 V and the resistance is 10 Ω?
1 W
10 W
100 W
0.1 W
Explanation - At resonance, current I = V/R = 10/10 = 1 A. Power P = I^2 R = 1^2 * 10 = 10 W.
Correct answer is: 10 W
Q.13 Which factor does NOT affect the resonant frequency of a circuit?
Inductance
Capacitance
Resistance
Voltage amplitude
Explanation - Resonant frequency depends only on L and C; resistance and voltage amplitude do not change it.
Correct answer is: Voltage amplitude
Q.14 At resonance, the voltage across which element is the highest in a series RLC circuit?
Resistor
Inductor
Capacitor
All elements equally
Explanation - At resonance, the current is maximum, but the voltage across L and C can be much higher than the source voltage, often leading to voltage magnification across them.
Correct answer is: Inductor
Q.15 What is the relationship between the quality factor Q and the damping factor δ in a series RLC circuit?
Q = δ
Q = 1/δ
Q = 1/(2δ)
Q = 2δ
Explanation - For a series RLC, δ = R/(2L) and Q = ω0 L / R, so Q = 1/(2δ/ω0).
Correct answer is: Q = 1/(2δ)
Q.16 Which of the following best describes a high-Q resonant circuit?
Broad bandwidth
Narrow bandwidth
High resistance
Low inductance
Explanation - A high Q factor implies low energy loss and a narrow resonance peak.
Correct answer is: Narrow bandwidth
Q.17 The energy stored in an inductor at resonance is equal to the energy stored in which component?
Resistor
Capacitor
Both resistor and capacitor
Neither
Explanation - At resonance, the energy alternates between the magnetic field of the inductor and the electric field of the capacitor.
Correct answer is: Capacitor
Q.18 Which circuit parameter is most affected when increasing the resistance in a series RLC circuit?
Resonant frequency
Bandwidth
Peak current
Capacitance
Explanation - Increasing R increases bandwidth Δf = R/(2πL), reducing Q.
Correct answer is: Bandwidth
Q.19 If the inductance of a series RLC circuit is doubled, how does the resonant frequency change?
It doubles
It halves
It remains the same
It increases by √2
Explanation - f0 = 1/(2π√(LC)) → f0 ∝ 1/√L, so doubling L halves f0.
Correct answer is: It halves
Q.20 What type of filter is typically designed using a series RLC resonant circuit?
Low-pass
High-pass
Band-pass
Band-stop
Explanation - A series RLC resonates at a specific frequency, passing frequencies near resonance while rejecting others.
Correct answer is: Band-pass
Q.21 In a parallel RLC circuit, the impedance at resonance is primarily dominated by which component?
Resistor
Inductor
Capacitor
None, it is infinite
Explanation - At resonance, the L and C paths provide infinite reactance, so the total impedance is infinite.
Correct answer is: None, it is infinite
Q.22 Which parameter must be adjusted to achieve a lower resonant frequency in an RLC circuit?
Increase capacitance
Decrease inductance
Increase resistance
Both A and B
Explanation - Lower f0 can be achieved by increasing C or decreasing L.
Correct answer is: Both A and B
Q.23 The resonant frequency of a 10 µH inductor and a 100 nF capacitor is closest to:
1 kHz
10 kHz
100 kHz
1 MHz
Explanation - f0 = 1/(2π√(LC)) ≈ 1/(2π√(10e-6 * 100e-9)) ≈ 1 MHz.
Correct answer is: 1 MHz
Q.24 Which statement about Q factor is true?
Q is always less than 1
Q = f0/Δf
Q depends on the source voltage
Q = Δf/f0
Explanation - Quality factor Q is defined as the ratio of resonant frequency to bandwidth: Q = f0/Δf.
Correct answer is: Q = f0/Δf
Q.25 In a resonant LC tank circuit, the stored energy oscillates between which two forms?
Kinetic and potential
Magnetic and electric
Thermal and electrical
Chemical and mechanical
Explanation - The energy alternates between the magnetic field of the inductor and the electric field of the capacitor.
Correct answer is: Magnetic and electric
Q.26 When an RLC circuit is driven at a frequency far above resonance, which component dominates the impedance?
Resistor
Inductor
Capacitor
Both L and C equally
Explanation - At high frequencies, inductive reactance XL = ωL becomes large, dominating the impedance.
Correct answer is: Inductor
Q.27 Which of the following is NOT a consequence of increasing the quality factor Q?
Narrower bandwidth
Higher peak current
Higher resonant voltage
Lower resonant frequency
Explanation - Increasing Q (by reducing R) does not change f0; it only sharpens the peak.
Correct answer is: Lower resonant frequency
Q.28 At resonance, the phase difference between source voltage and current in a series RLC circuit is:
0°
90°
-90°
180°
Explanation - At resonance, the reactances cancel, leaving a purely resistive impedance, so voltage and current are in phase.
Correct answer is: 0°
Q.29 If the resistance in a series RLC circuit is increased, the amplitude of the resonant voltage across the inductor:
Increases
Decreases
Remains unchanged
Becomes zero
Explanation - Higher R reduces current at resonance, thereby reducing the voltage across L.
Correct answer is: Decreases
Q.30 In a parallel RLC circuit, what is the total admittance at resonance?
Zero
Purely resistive
Purely inductive
Purely capacitive
Explanation - At resonance, the reactive parts cancel, leaving only the resistor's conductance.
Correct answer is: Purely resistive
Q.31 Which of these is a common application of a resonant RLC circuit?
Power supply filtering
Signal generation
Magnetic field sensing
All of the above
Explanation - Resonant circuits are used for tuning, filtering, and in oscillators.
Correct answer is: All of the above
Q.32 In a series RLC circuit, the phase angle φ between voltage and current at frequency f is:
tan⁻¹((XL - XC)/R)
tan⁻¹(R/(XL - XC))
tan⁻¹((XC - XL)/R)
tan⁻¹(R/(XC - XL))
Explanation - The phase angle is given by φ = arctan((XL - XC)/R).
Correct answer is: tan⁻¹((XL - XC)/R)
Q.33 Which of the following changes will increase the bandwidth of a parallel RLC circuit?
Increasing resistance
Decreasing resistance
Increasing inductance
Increasing capacitance
Explanation - For a parallel RLC, bandwidth Δf = R/(2πL), so higher R widens bandwidth.
Correct answer is: Increasing resistance
Q.34 The resonant frequency of an LC tank circuit is primarily determined by:
Resistor value
Inductor value
Capacitor value
Both inductance and capacitance
Explanation - f0 depends solely on L and C: f0 = 1/(2π√(LC)).
Correct answer is: Both inductance and capacitance
Q.35 When the circuit is at resonance, the reactive power stored in the inductor equals:
Zero
The active power
The reactive power in the capacitor
The sum of reactive powers
Explanation - Reactive power oscillates between L and C; they are equal and opposite.
Correct answer is: The reactive power in the capacitor
Q.36 Which of the following best describes the shape of the impedance magnitude vs. frequency curve for a series RLC circuit?
A peak at resonance
A dip at resonance
A flat line
A constant rise
Explanation - In series, impedance is minimum at resonance, but the magnitude of current has a peak; impedance curve shows a trough.
Correct answer is: A peak at resonance
Q.37 If the resistance in a series RLC circuit is very small, what happens to the voltage across the capacitor at resonance?
It becomes very large
It becomes equal to the source voltage
It becomes zero
It equals the voltage across the inductor
Explanation - Low R leads to high current, which magnifies voltages across L and C at resonance.
Correct answer is: It becomes very large
Q.38 Resonance in a circuit leads to:
Maximum impedance
Minimum impedance
Zero power dissipation
Both B and C
Explanation - Resonance minimizes impedance and maximizes current, but power dissipation in the resistor remains the same as at other frequencies.
Correct answer is: Both B and C
Q.39 Which parameter directly affects the height of the resonance peak in a series RLC circuit?
Inductor value
Capacitor value
Resistance value
Source voltage
Explanation - Lower resistance yields a higher peak current and voltage magnification.
Correct answer is: Resistance value
Q.40 A series RLC circuit with R=10 Ω, L=100 µH, and C=10 µF has a resonant frequency of:
50 Hz
158 Hz
500 Hz
1580 Hz
Explanation - f0 = 1/(2π√(LC)) ≈ 1/(2π√(100e-6 * 10e-6)) ≈ 158 Hz.
Correct answer is: 158 Hz
Q.41 The total power factor of a series RLC circuit at resonance is:
0
0.5
1
Undefined
Explanation - At resonance, impedance is purely resistive, so power factor cos(0) = 1.
Correct answer is: 1
Q.42 Which of the following is true regarding the energy loss in a resonant circuit?
Energy loss is maximum at resonance
Energy loss is zero at resonance
Energy loss is the same at all frequencies
Energy loss depends only on L
Explanation - In an ideal lossless LC tank, no energy is lost at resonance; in real circuits, loss is due to resistance.
Correct answer is: Energy loss is zero at resonance
Q.43 Which frequency range does a resonant RLC circuit typically select in a radio receiver?
The entire spectrum
A narrow band around the carrier frequency
Only DC
Only high frequencies above 1 GHz
Explanation - Resonant circuits act as band‑pass filters, selecting a narrow frequency band.
Correct answer is: A narrow band around the carrier frequency
Q.44 A parallel RLC circuit at resonance can be used as:
A voltage amplifier
A current sink
A filter
All of the above
Explanation - Parallel resonant circuits are used as band-stop or band-pass filters.
Correct answer is: A filter
Q.45 In a series RLC circuit, the peak current at resonance is given by:
I = V0 / R
I = V0 / √(R^2 + (XL-XC)^2)
I = V0 * R
I = V0 / (XL + XC)
Explanation - At resonance XL = XC, so impedance is R, giving I = V0/R.
Correct answer is: I = V0 / R
Q.46 The quality factor Q for a parallel RLC circuit is defined as:
Q = R / (ω0 L)
Q = ω0 L / R
Q = 1 / (ω0 R C)
Q = ω0 C R
Explanation - For parallel RLC, Q = R / (ω0 L) or equivalently Q = ω0 C R.
Correct answer is: Q = R / (ω0 L)
Q.47 Which of the following best describes the impedance of a parallel RLC circuit at resonance?
Minimum
Maximum
Zero
Infinite
Explanation - At resonance, the parallel impedance is maximum because the L and C paths cancel each other out.
Correct answer is: Maximum
Q.48 If a circuit is operating at resonance, which of these statements is true regarding the reactive components?
Their reactive powers cancel each other out
The inductor stores all the energy
The capacitor stores all the energy
Both store energy but neither supplies any power
Explanation - In resonance, the reactive power from L and C are equal and opposite, so net reactive power is zero.
Correct answer is: Their reactive powers cancel each other out
Q.49 Which of the following parameters is not directly involved in calculating the resonant frequency?
Inductance
Capacitance
Resistance
Angular frequency
Explanation - Resonant frequency depends only on L and C; resistance does not affect it.
Correct answer is: Resistance
Q.50 What is the effect of adding a parallel resistor across an LC tank circuit?
It increases the Q factor
It decreases the Q factor
It shifts the resonant frequency
It has no effect
Explanation - A parallel resistor provides a path for energy dissipation, lowering the Q.
Correct answer is: It decreases the Q factor
Q.51 The bandwidth of a parallel RLC circuit can be expressed as:
Δf = R/(2πL)
Δf = L/(2πR)
Δf = R/(2πC)
Δf = C/(2πR)
Explanation - For a parallel RLC, bandwidth Δf = R/(2πL).
Correct answer is: Δf = R/(2πL)
Q.52 Which of the following would increase the resonant frequency of a series RLC circuit?
Increase L
Increase C
Decrease L
Increase R
Explanation - Reducing inductance raises the resonant frequency f0 = 1/(2π√(LC)).
Correct answer is: Decrease L
Q.53 In a series RLC circuit, if the source voltage is increased, what happens to the resonant frequency?
It increases
It decreases
It remains unchanged
It oscillates
Explanation - Resonant frequency depends only on L and C, not on source voltage.
Correct answer is: It remains unchanged
Q.54 The energy stored in a capacitor at resonance is given by:
1/2 C V^2
1/2 L I^2
C V
L I
Explanation - Energy stored in a capacitor is W = 1/2 C V^2.
Correct answer is: 1/2 C V^2
Q.55 Which component has the highest impedance at resonance in a series RLC circuit?
Resistor
Inductor
Capacitor
All equal
Explanation - At resonance, impedance is purely resistive; inductive and capacitive reactances cancel.
Correct answer is: Resistor
Q.56 In a parallel RLC circuit, the total current drawn from the source at resonance is:
Maximum
Minimum
Same as at DC
Undefined
Explanation - At resonance, the reactive currents through L and C cancel, leaving only the resistor current, which is maximum for that source voltage.
Correct answer is: Maximum
Q.57 The formula for the resonant frequency of an RLC circuit can be approximated by:
f0 = 1/(2πLC)
f0 = 1/(2π√(LC))
f0 = √(LC)/(2π)
f0 = √(L/C)/(2π)
Explanation - Resonant frequency depends on the product of inductance and capacitance under a square root.
Correct answer is: f0 = 1/(2π√(LC))
Q.58 When the Q factor of a resonant circuit is high, what does that indicate about energy dissipation?
Energy dissipation is high
Energy dissipation is low
Energy dissipation is zero
Energy dissipation is infinite
Explanation - High Q means low energy loss per cycle.
Correct answer is: Energy dissipation is low
Q.59 Which type of filter is formed by a series RLC circuit that allows only frequencies close to f0 to pass?
Low-pass
High-pass
Band-pass
Band-stop
Explanation - A series RLC acts as a band‑pass filter.
Correct answer is: Band-pass
Q.60 Which of the following is a typical application of a resonant LC circuit in electronics?
Oscillator
Amplifier
Power supply
All of the above
Explanation - Resonant LC circuits are key components of oscillators.
Correct answer is: Oscillator
Q.61 What happens to the quality factor Q when resistance is increased in a series RLC circuit?
Q increases
Q decreases
Q stays the same
Q becomes zero
Explanation - Q = ω0 L / R; increasing R decreases Q.
Correct answer is: Q decreases
Q.62 At resonance in a series RLC circuit, the power dissipated in the resistor is maximum. If the source voltage is 12 V and R = 4 Ω, the power dissipated is:
4 W
36 W
12 W
24 W
Explanation - P = V^2 / R = (12^2)/4 = 144/4 = 36 W.
Correct answer is: 36 W
Q.63 Which parameter determines the sharpness of the resonance peak in a circuit?
Inductance
Capacitance
Quality factor Q
Resonant frequency
Explanation - Higher Q results in a sharper, more pronounced resonance peak.
Correct answer is: Quality factor Q
Q.64 In a parallel RLC circuit, the resonant frequency is affected by:
Only inductance
Only capacitance
Both inductance and capacitance
Neither inductance nor capacitance
Explanation - f0 = 1/(2π√(LC)) for both series and parallel circuits.
Correct answer is: Both inductance and capacitance
Q.65 Which of the following is NOT a characteristic of an ideal resonant circuit?
Infinite Q factor
Zero energy loss
Infinite current at resonance
Finite voltage across components
Explanation - An ideal resonant circuit would have zero resistance, leading to infinite current, but this is not physically realizable.
Correct answer is: Infinite current at resonance
Q.66 Resonant frequency of a circuit can be tuned by changing which of the following?
Only L
Only C
Either L or C
Only R
Explanation - Changing either inductance or capacitance shifts the resonant frequency.
Correct answer is: Either L or C
Q.67 What is the significance of a high Q factor in an RF filter?
Broad bandwidth
Narrow bandwidth
Higher power consumption
Lower selectivity
Explanation - High Q means the filter allows only a narrow range of frequencies to pass.
Correct answer is: Narrow bandwidth
Q.68 At resonance, the total energy stored in an LC circuit is:
Maximum
Minimum
Zero
Constant over time
Explanation - Energy oscillates between L and C but the total remains constant; its maximum magnitude is at resonance when the amplitude is greatest.
Correct answer is: Maximum
Q.69 The power factor of a series RLC circuit at resonance is:
Zero
0.5
1
Negative
Explanation - At resonance, current and voltage are in phase, giving a power factor of 1.
Correct answer is: 1
Q.70 Which of the following describes the impedance of a parallel RLC circuit at resonance?
Zero
Maximum
Equal to R
Equal to L + C
Explanation - At resonance, the parallel impedance is very high (ideally infinite).
Correct answer is: Maximum
Q.71 A resonant tank circuit is used in a radio transmitter to:
Stabilize the carrier frequency
Amplify the signal
Reduce power consumption
Filter out noise
Explanation - The resonant tank provides a stable oscillation frequency.
Correct answer is: Stabilize the carrier frequency
Q.72 The bandwidth of a series RLC circuit is directly proportional to which parameter?
Inductance
Capacitance
Resistance
Resonant frequency
Explanation - Bandwidth Δf = R/(2πL); higher R yields wider bandwidth.
Correct answer is: Resistance
Q.73 Which component provides energy storage in a resonant RLC circuit?
Resistor
Inductor
Capacitor
Both Inductor and Capacitor
Explanation - Both L and C store energy in magnetic and electric fields respectively.
Correct answer is: Both Inductor and Capacitor
Q.74 If the resistance in a series RLC circuit is increased, the resonant frequency:
Increases
Decreases
Stays the same
Oscillates
Explanation - Resonant frequency depends only on L and C, not on R.
Correct answer is: Stays the same
Q.75 Which of the following is NOT an effect of increasing the capacitance in an RLC circuit?
Lower resonant frequency
Higher Q factor
Increased bandwidth
Lower resonant frequency
Explanation - Increasing C lowers f0 and increases bandwidth; Q may change depending on R.
Correct answer is: Higher Q factor
Q.76 At resonance, the impedance of a series RLC circuit is:
Zero
Maximum
Purely resistive
Purely reactive
Explanation - Inductive and capacitive reactances cancel, leaving only the resistor.
Correct answer is: Purely resistive
Q.77 Which formula gives the bandwidth of a parallel RLC circuit?
Δf = R/(2πL)
Δf = L/(2πR)
Δf = R/(2πC)
Δf = C/(2πR)
Explanation - For a parallel RLC, Δf = R/(2πL).
Correct answer is: Δf = R/(2πL)
Q.78 What is the primary role of a resonant circuit in a tuning fork?
To store energy
To provide a stable frequency
To dissipate heat
To amplify sound
Explanation - A tuning fork resonates at its natural frequency, producing a stable tone.
Correct answer is: To provide a stable frequency
Q.79 In a resonant circuit, the term 'bandwidth' refers to:
The range of frequencies where voltage is maximum
The range of frequencies where power is zero
The range of frequencies where impedance is minimal
The range of frequencies around f0 where impedance is within a factor of √2 of its minimum
Explanation - Bandwidth is the width between the points where impedance rises to √2 times its minimum (or where power falls to half its peak).
Correct answer is: The range of frequencies around f0 where impedance is within a factor of √2 of its minimum
Q.80 Which component in a resonant circuit is primarily responsible for determining the phase shift between voltage and current?
Resistor
Inductor
Capacitor
Both Inductor and Capacitor
Explanation - Inductive and capacitive reactances produce phase shifts; they cancel at resonance.
Correct answer is: Both Inductor and Capacitor
Q.81 At resonance, the current through a series RLC circuit is:
Zero
Maximum
Same as the resistor current
Same as the capacitor current
Explanation - Impedance is minimum, so current is maximum.
Correct answer is: Maximum
Q.82 A parallel RLC circuit can act as a notch filter because at resonance it:
Allows all frequencies to pass
Blocks a narrow band of frequencies
Blocks all frequencies
Amplifies a narrow band of frequencies
Explanation - At resonance, impedance is very high, so very little current flows at that frequency.
Correct answer is: Blocks a narrow band of frequencies
Q.83 The formula for the resonant frequency of a series RLC circuit is:
f0 = √(L/C)
f0 = 1/(2π√(LC))
f0 = 1/(LC)
f0 = √(LC)/(2π)
Explanation - Resonant frequency depends on the product of L and C under a square root.
Correct answer is: f0 = 1/(2π√(LC))
Q.84 Which parameter increases the quality factor Q of a series RLC circuit?
Increasing resistance
Increasing inductance
Increasing capacitance
All of the above
Explanation - Q = ω0 L / R; increasing L increases Q.
Correct answer is: Increasing inductance
Q.85 Resonance in a circuit results in the maximum power delivered to the:
Resistor
Inductor
Capacitor
All of the above
Explanation - At resonance, current is maximum and thus the power dissipated in the resistor is maximum.
Correct answer is: Resistor
Q.86 Which of the following is a real-world example of a resonant circuit?
A battery
An incandescent lamp
A tuning fork
A resistor
Explanation - A tuning fork has a natural resonant frequency.
Correct answer is: A tuning fork
Q.87 statement: In a parallel RLC circuit, the total impedance is minimum at resonance.
True
False
Not sure
Both
Explanation - At resonance, the impedance is maximum (ideally infinite).
Correct answer is: False
Q.88 Which of the following best describes the impedance of an inductor?
Z = R
Z = jωL
Z = 1/(jωC)
Z = R + jωL
Explanation - Inductor impedance is purely imaginary: jωL.
Correct answer is: Z = jωL
Q.89 When the source frequency is less than the resonant frequency of a series RLC circuit, the circuit behaves as:
Capacitive
Inductive
Resistive
Neutral
Explanation - Below resonance, capacitive reactance dominates, making the circuit capacitive.
Correct answer is: Capacitive
Q.90 Which of the following parameters does NOT affect the energy stored in an inductor?
Inductance
Current
Frequency
Resistor value
Explanation - Energy stored is 1/2 L I^2; resistance does not appear.
Correct answer is: Resistor value
Q.91 Which of the following best describes the voltage across a capacitor in a resonant LC tank at steady state?
Zero
Maximum at resonance
Minimum at resonance
Same as source voltage
Explanation - Voltage across capacitor can be higher than source at resonance due to resonant magnification.
Correct answer is: Maximum at resonance
Q.92 What is the effect of adding a small series resistor to an LC tank circuit?
Increases Q
Decreases Q
Shifts resonant frequency
Has no effect
Explanation - The resistor introduces loss, lowering the Q factor.
Correct answer is: Decreases Q
Q.93 The reactive power stored in a capacitor is given by:
Q = 1/(2π f C)
Q = 2π f C
Q = V^2 / (2π f C)
Q = V^2 * 2π f C
Explanation - Reactive power in a capacitor is Q = 2π f C V^2.
Correct answer is: Q = 2π f C
Q.94 Which of the following statements is true about a resonant tank circuit?
It dissipates energy at all times
It stores energy in both magnetic and electric fields
It has zero voltage across its components at resonance
It only works at DC
Explanation - An ideal tank oscillates between magnetic and electric energy storage.
Correct answer is: It stores energy in both magnetic and electric fields
Q.95 In a series RLC circuit, the current at resonance is:
I = V/R
I = V/(XL + XC)
I = 0
I = V/(XL - XC)
Explanation - At resonance, XL = XC, so impedance is R only.
Correct answer is: I = V/R
Q.96 Which of the following is a typical application of a band-stop (notch) filter?
Removing a specific interference frequency
Amplifying audio signals
Power conditioning
Signal mixing
Explanation - Band-stop filters block a narrow frequency band.
Correct answer is: Removing a specific interference frequency
Q.97 If an RLC circuit is tuned to a higher frequency, what must happen to the inductance or capacitance?
Increase inductance and increase capacitance
Decrease inductance and increase capacitance
Increase inductance and decrease capacitance
Decrease inductance and decrease capacitance
Explanation - f0 ∝ 1/√(LC); reducing both L and C raises f0.
Correct answer is: Decrease inductance and decrease capacitance
Q.98 Which of the following correctly represents the impedance of a capacitor?
Z = R
Z = jωL
Z = 1/(jωC)
Z = R + jωL
Explanation - Capacitive impedance is inversely proportional to frequency and capacitance.
Correct answer is: Z = 1/(jωC)
Q.99 The energy stored in an inductor at resonance is:
Equal to that stored in the capacitor
Zero
Double the energy in the capacitor
Independent of current
Explanation - At resonance, energy oscillates between L and C, storing equal amounts at any instant.
Correct answer is: Equal to that stored in the capacitor
Q.100 Which of the following is a direct consequence of a high Q factor?
Wide bandwidth
Large phase shift
Sharp resonance peak
High power dissipation
Explanation - High Q implies less energy loss and a sharp, narrow resonance.
Correct answer is: Sharp resonance peak
Q.101 A resonant circuit can be used to generate:
DC voltage
AC voltage
A stable frequency
Random noise
Explanation - Resonant circuits naturally oscillate at their resonant frequency.
Correct answer is: A stable frequency
Q.102 In a parallel RLC circuit, the total current drawn from the source at resonance is:
Zero
Maximum
Equal to the resistor current
Minimum
Explanation - At resonance, reactive currents cancel, leaving only the resistor current, which is maximal for the given source voltage.
Correct answer is: Maximum
Q.103 Which of these statements is true about the quality factor Q for a series RLC circuit?
Q = ω0 L / R
Q = R / (ω0 L)
Q = ω0 C R
Q = 1/(ω0 C R)
Explanation - Q = ω0 L / R for series RLC, where ω0 = 2πf0.
Correct answer is: Q = ω0 L / R
Q.104 When the frequency of a source is much lower than the resonant frequency of a series RLC circuit, the circuit behaves as:
Inductive
Capacitive
Resistive
Neutral
Explanation - At low frequencies, capacitive reactance is large, dominating the circuit.
Correct answer is: Capacitive
Q.105 What is the resonant frequency of a 4 µH inductor and a 1 µF capacitor?
20 kHz
31.6 kHz
50 kHz
100 kHz
Explanation - f0 = 1/(2π√(LC)) ≈ 1/(2π√(4e-6 * 1e-6)) ≈ 31.6 kHz.
Correct answer is: 31.6 kHz
Q.106 Which of the following is a parameter that determines the bandwidth of a parallel RLC circuit?
Inductor value
Capacitor value
Resistance value
Resonant frequency
Explanation - Bandwidth Δf = R/(2πL) for parallel RLC.
Correct answer is: Resistance value
Q.107 If the resistance in a resonant circuit is increased, the Q factor:
Increases
Decreases
Remains unchanged
Becomes infinite
Explanation - Higher resistance dissipates energy faster, lowering Q.
Correct answer is: Decreases
Q.108 In a resonant tank circuit, the maximum current occurs when:
The source frequency is far above resonance
The source frequency is far below resonance
The source frequency equals the resonant frequency
The source voltage is zero
Explanation - At resonance, impedance is minimum and current is maximum.
Correct answer is: The source frequency equals the resonant frequency
Q.109 A resonant RLC circuit can be used to:
Create a DC supply
Filter out unwanted frequencies
Store energy indefinitely
Increase resistance
Explanation - Resonant circuits can be used as band-pass or band-stop filters.
Correct answer is: Filter out unwanted frequencies
Q.110 Which of the following equations represents the impedance of a parallel RLC circuit at resonance?
Z = R
Z = R/(1 + jQ)
Z = R/(1 - jQ)
Z = R * (1 + jQ)
Explanation - At resonance, the reactive parts cancel, leaving the resistor as the only impedance.
Correct answer is: Z = R
Q.111 The quality factor Q of a parallel RLC circuit is given by:
Q = R/(ω0 L)
Q = ω0 L / R
Q = ω0 C R
Q = 1/(ω0 C R)
Explanation - Q for parallel RLC is R/(ω0 L).
Correct answer is: Q = R/(ω0 L)
Q.112 If a series RLC circuit is operating at resonance, the phase shift between voltage and current is:
0°
90°
-90°
180°
Explanation - At resonance, impedance is purely resistive, so voltage and current are in phase.
Correct answer is: 0°
Q.113 Which of the following best describes the impedance of a capacitor?
Z = jωL
Z = 1/(jωC)
Z = R
Z = R + jωL
Explanation - Capacitive impedance is inversely proportional to frequency and capacitance.
Correct answer is: Z = 1/(jωC)
Q.114 In a series RLC circuit, the bandwidth Δf is given by:
Δf = R/(2πL)
Δf = L/(2πR)
Δf = R/(2πC)
Δf = C/(2πR)
Explanation - The bandwidth of a series RLC is Δf = R/(2πL).
Correct answer is: Δf = R/(2πL)
Q.115 The resonant frequency of an RLC circuit is independent of:
Inductance
Capacitance
Resistance
All of the above
Explanation - Resonant frequency depends only on L and C.
Correct answer is: Resistance
Q.116 The resonant frequency of a 50 µH inductor and a 10 nF capacitor is:
5 kHz
15 kHz
30 kHz
50 kHz
Explanation - f0 = 1/(2π√(LC)) ≈ 5 kHz.
Correct answer is: 5 kHz
Q.117 Which of the following parameters directly increases the Q factor of a parallel RLC circuit?
Increase resistance
Increase inductance
Decrease capacitance
All of the above
Explanation - For parallel RLC, Q = R/(ω0 L); increasing R increases Q.
Correct answer is: Increase resistance
Q.118 At resonance in a parallel RLC circuit, the total current drawn from the source is:
Zero
Maximum
Minimum
Equal to the source voltage
Explanation - At resonance, the reactive currents cancel, leaving only the small resistor current.
Correct answer is: Minimum
Q.119 Which of these is an example of a resonant circuit used in radio receivers?
Transistor amplifier
LC tank circuit
Resistor network
Diode rectifier
Explanation - LC tanks are used for tuning and frequency selection.
Correct answer is: LC tank circuit
Q.120 When the source frequency is equal to the resonant frequency of a parallel RLC circuit, the impedance of the circuit:
Is minimum
Is maximum
Is equal to R
Is purely reactive
Explanation - At resonance, the parallel impedance is maximum (ideally infinite).
Correct answer is: Is maximum
Q.121 Which component in an RLC circuit stores energy in a magnetic field?
Resistor
Inductor
Capacitor
Both Inductor and Capacitor
Explanation - Inductors store energy in magnetic fields.
Correct answer is: Inductor
Q.122 In a resonant circuit, the bandwidth Δf is related to Q and f0 by:
Δf = Q / f0
Δf = f0 / Q
Δf = Q * f0
Δf = f0 * Q^2
Explanation - By definition, Q = f0/Δf.
Correct answer is: Δf = f0 / Q
Q.123 Which of the following statements is true about resonant circuits in the presence of loss?
Resonant frequency shifts significantly
Quality factor remains unchanged
Resonant frequency shifts slightly, Q decreases
Both resonance frequency and Q are unaffected
Explanation - Losses can slightly alter the resonant frequency and always reduce Q.
Correct answer is: Resonant frequency shifts slightly, Q decreases
Q.124 The resonant frequency of a 5 µH inductor and a 2 µF capacitor is:
6.3 kHz
7.9 kHz
9.5 kHz
10.5 kHz
Explanation - f0 = 1/(2π√(LC)) ≈ 6.3 kHz.
Correct answer is: 6.3 kHz
Q.125 At resonance, the reactive power stored in the capacitor equals:
Zero
Maximum
Minimum
Half the stored reactive power in the inductor
Explanation - The capacitor stores reactive power equal to the inductive reactive power at resonance.
Correct answer is: Maximum
Q.126 Which of the following is a property of an ideal inductor?
It has no resistance
It dissipates power
It behaves like a capacitor
It has zero reactance
Explanation - An ideal inductor only has inductive reactance and no resistance.
Correct answer is: It has no resistance
Q.127 Which of the following is a characteristic of a series RLC circuit at resonance?
Current is zero
Voltage across L equals voltage across C
Impedance is infinite
Resonant frequency is zero
Explanation - At resonance, the magnitudes of voltage across L and C are equal and opposite.
Correct answer is: Voltage across L equals voltage across C
Q.128 Which of the following would decrease the bandwidth of a parallel RLC circuit?
Increasing resistance
Decreasing inductance
Decreasing capacitance
Increasing resistance and decreasing inductance
Explanation - Bandwidth Δf = R/(2πL); decreasing L increases bandwidth, so to decrease bandwidth, increase L or decrease R.
Correct answer is: Decreasing inductance
Q.129 Which component provides the reactive energy storage in a resonant tank?
Resistor
Inductor
Capacitor
Both Inductor and Capacitor
Explanation - Both store energy in magnetic and electric fields.
Correct answer is: Both Inductor and Capacitor
Q.130 In a parallel RLC circuit, the current through the resistor at resonance is:
Zero
Maximum
Minimum
The same as the source current
Explanation - At resonance, the large impedance of L and C reduces total current; only a small resistor current flows.
Correct answer is: Minimum
Q.131 The resonant frequency of an L-C combination of 20 µH and 1 µF is approximately:
3.5 kHz
5 kHz
7 kHz
10 kHz
Explanation - f0 = 1/(2π√(20e-6 * 1e-6)) ≈ 7 kHz.
Correct answer is: 7 kHz
Q.132 What is the relationship between the resonant frequency and the quality factor for a series RLC circuit?
f0 = Q * Δf
f0 = Δf / Q
Q = f0 / Δf
Q = Δf / f0
Explanation - Definition of quality factor: Q = f0 / Δf.
Correct answer is: Q = f0 / Δf
Q.133 Which of the following is NOT a typical application of a resonant circuit?
Signal filtering
Oscillation generation
Voltage regulation
Frequency tuning
Explanation - Resonant circuits are not used for voltage regulation; they are used for filtering, tuning, and generating oscillations.
Correct answer is: Voltage regulation
Q.134 When the resistance in a series RLC circuit is very high, the resonant circuit behaves like:
A perfect capacitor
A perfect inductor
A high-Q tank
A low-Q tank
Explanation - High resistance reduces losses, increasing Q.
Correct answer is: A high-Q tank
Q.135 In a resonant tank circuit, the maximum current is limited by:
Inductor value
Capacitor value
Source voltage
Both source voltage and resistance
Explanation - Current is limited by source voltage and the small resistance in the circuit.
Correct answer is: Both source voltage and resistance
Q.136 The formula for resonant frequency in an RLC circuit is f0 = 1/(2π√(LC)). Which unit must L and C be in for f0 to be in Hz?
Henrys and Farads
Ohms and Volts
Henrys and Ohms
Farads and Ohms
Explanation - L in Henrys and C in Farads produce frequency in Hz.
Correct answer is: Henrys and Farads
Q.137 What happens to the phase angle between voltage and current in a series RLC circuit as frequency increases from below resonance to above resonance?
It increases from negative to positive
It remains constant
It decreases from positive to negative
It jumps directly to 90°
Explanation - Below resonance, phase lag (negative); above resonance, phase lead (positive).
Correct answer is: It increases from negative to positive
Q.138 In a parallel RLC circuit, the resonant frequency is most sensitive to changes in:
Inductance
Capacitance
Resistance
All of the above
Explanation - Frequency depends on L and C; resistance influences Q but not f0 directly.
Correct answer is: All of the above
Q.139 Which of the following describes the impedance of a parallel RLC circuit at frequencies far from resonance?
Very high
Very low
Equal to R
Zero
Explanation - Far from resonance, either inductive or capacitive reactance dominates, creating low impedance.
Correct answer is: Very low
Q.140 In a resonant LC tank, the energy oscillates between magnetic and electric forms. Which statement best describes this energy transfer?
Energy is lost as heat at each cycle
Energy flows back and forth without loss
Energy accumulates in the inductor only
Energy is stored only in the capacitor
Explanation - In an ideal tank, energy is exchanged between L and C with no loss.
Correct answer is: Energy flows back and forth without loss
Q.141 Which of the following would NOT shift the resonant frequency of a series RLC circuit?
Adding a parallel resistor
Changing the capacitor value
Changing the inductor value
Changing the source voltage
Explanation - A parallel resistor does not affect the resonant frequency, only the Q.
Correct answer is: Adding a parallel resistor
Q.142 The bandwidth Δf of a parallel RLC circuit is directly proportional to:
Resistance
Inductance
Capacitance
Resonant frequency
Explanation - Δf = R/(2πL); higher R increases Δf.
Correct answer is: Resistance
Q.143 The reactive power in a resonant LC tank is zero. Which of the following is true?
The reactive power in the inductor equals the reactive power in the capacitor
All reactive power is dissipated in the resistor
There is no reactive power in the tank
Reactive power is infinite
Explanation - They cancel each other out at resonance.
Correct answer is: The reactive power in the inductor equals the reactive power in the capacitor