Q. In an RLC series circuit, what is the condition for resonance?
A.
XL = XC
B.
R = 0
C.
XL > XC
D.
R > XL
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Solution
Resonance in an RLC series circuit occurs when the inductive reactance (X_L) equals the capacitive reactance (X_C), i.e., X_L = X_C.
Correct Answer:
A
— XL = XC
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Q. The power factor of an AC circuit is defined as the ratio of:
A.
Real power to apparent power
B.
Apparent power to real power
C.
Voltage to current
D.
Current to voltage
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Solution
The power factor is defined as the ratio of real power to apparent power.
Correct Answer:
A
— Real power to apparent power
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Q. What is the average power consumed in an AC circuit with a power factor of 0.8 and an RMS voltage of 100 V with a current of 5 A?
A.
200 W
B.
400 W
C.
300 W
D.
500 W
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Solution
Average power (P) is given by P = V_rms * I_rms * PF. Therefore, P = 100 V * 5 A * 0.8 = 400 W.
Correct Answer:
C
— 300 W
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Q. What is the average power consumed in an AC circuit with a power factor of 0.8 and a maximum power of 100 W?
A.
80 W
B.
100 W
C.
120 W
D.
160 W
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Solution
Average power (P_avg) is given by P_avg = P_max × power factor. Therefore, P_avg = 100 W × 0.8 = 80 W.
Correct Answer:
A
— 80 W
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Q. What is the effect of increasing the capacitance in a capacitor in an AC circuit on the current?
A.
Increases current
B.
Decreases current
C.
No effect
D.
Current becomes zero
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Solution
Increasing the capacitance (C) decreases the capacitive reactance (X_C), which increases the current (I) in the circuit.
Correct Answer:
A
— Increases current
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Q. What is the effect of increasing the capacitance in an AC circuit on the capacitive reactance?
A.
Increases
B.
Decreases
C.
Remains the same
D.
Becomes zero
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Solution
Capacitive reactance (X_C) is given by X_C = 1/(2πfC). Increasing capacitance (C) decreases X_C.
Correct Answer:
B
— Decreases
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Q. What is the effect of increasing the capacitance in an AC circuit on the phase angle between voltage and current?
A.
Increases phase angle
B.
Decreases phase angle
C.
No effect
D.
Phase angle becomes 90 degrees
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Solution
Increasing capacitance decreases the phase angle between voltage and current in an AC circuit.
Correct Answer:
B
— Decreases phase angle
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Q. What is the effect of increasing the frequency on the capacitive reactance?
A.
Increases
B.
Decreases
C.
Remains the same
D.
Becomes zero
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Solution
Capacitive reactance X_C = 1/(ωC) decreases with increasing frequency.
Correct Answer:
B
— Decreases
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Q. What is the effect of increasing the frequency on the impedance of a series RLC circuit?
A.
Increases
B.
Decreases
C.
Remains constant
D.
Depends on R, L, and C
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Solution
The impedance (Z) of a series RLC circuit depends on the values of resistance (R), inductance (L), capacitance (C), and frequency (f). As frequency increases, the inductive reactance increases and capacitive reactance decreases, affecting the total impedance.
Correct Answer:
D
— Depends on R, L, and C
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Q. What is the effect of increasing the frequency on the impedance of an inductor?
A.
Increases
B.
Decreases
C.
Remains the same
D.
Becomes zero
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Solution
The impedance of an inductor (Z_L) increases with frequency, as Z_L = jωL, where ω = 2πf.
Correct Answer:
A
— Increases
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Q. What is the effect of increasing the resistance in a series AC circuit?
A.
Increases current
B.
Decreases current
C.
No effect
D.
Increases voltage
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Solution
Increasing the resistance in a series AC circuit decreases the current.
Correct Answer:
B
— Decreases current
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Q. What is the effect of increasing the resistance in a series RLC circuit on the Q factor?
A.
Increases Q factor
B.
Decreases Q factor
C.
No effect
D.
Doubles Q factor
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Solution
Increasing resistance decreases the Q factor, which is defined as Q = ωL/R.
Correct Answer:
B
— Decreases Q factor
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Q. What is the effect of increasing the resistance in an AC circuit on the overall current?
A.
Increases current
B.
Decreases current
C.
No effect
D.
Doubles current
Show solution
Solution
According to Ohm's law, increasing resistance in an AC circuit decreases the overall current.
Correct Answer:
B
— Decreases current
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Q. What is the formula for calculating the total power in a series RLC circuit?
A.
P = VI
B.
P = I^2R
C.
P = V^2/R
D.
P = VI cos(φ)
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Solution
The total power in a series RLC circuit is given by P = VI cos(φ), where φ is the phase angle.
Correct Answer:
D
— P = VI cos(φ)
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Q. What is the formula for calculating the total power in an AC circuit with a power factor?
A.
P = VI
B.
P = VI cos(φ)
C.
P = VI sin(φ)
D.
P = V^2/R
Show solution
Solution
The total power in an AC circuit is given by P = VI cos(φ), where φ is the phase angle.
Correct Answer:
B
— P = VI cos(φ)
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Q. What is the formula for the total power in a series RLC circuit?
A.
P = VI
B.
P = I^2R
C.
P = V^2/R
D.
P = VI cos(φ)
Show solution
Solution
The total power in a series RLC circuit is given by P = VI cos(φ), where φ is the phase angle.
Correct Answer:
D
— P = VI cos(φ)
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Q. What is the impedance of a series circuit containing a resistor (R) and an inductor (L)?
A.
R
B.
√(R^2 + (ωL)^2)
C.
R + ωL
D.
R - ωL
Show solution
Solution
The impedance Z = √(R^2 + (ωL)^2) in a series R-L circuit.
Correct Answer:
B
— √(R^2 + (ωL)^2)
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Q. What is the impedance of a series circuit containing a resistor and an inductor?
A.
R
B.
√(R^2 + (ωL)^2)
C.
R + jωL
D.
R - jωL
Show solution
Solution
The impedance Z in a series R-L circuit is given by Z = √(R^2 + (ωL)^2).
Correct Answer:
B
— √(R^2 + (ωL)^2)
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Q. What is the impedance of a series RLC circuit at resonance?
Show solution
Solution
At resonance, the impedance of a series RLC circuit is equal to the resistance R.
Correct Answer:
A
— R
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Q. What is the power factor in a circuit with a phase angle of 60 degrees?
A.
0.5
B.
0.866
C.
1
D.
0
Show solution
Solution
The power factor is cos(60°) = 0.5.
Correct Answer:
B
— 0.866
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Q. What is the power factor of a circuit with a phase angle of 60 degrees?
A.
0.5
B.
0.866
C.
1
D.
0.707
Show solution
Solution
The power factor (PF) is given by cos(θ). For a phase angle of 60 degrees, PF = cos(60°) = 0.5.
Correct Answer:
B
— 0.866
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Q. What is the power factor of an AC circuit with a phase angle of 60 degrees?
A.
0.5
B.
0.866
C.
1
D.
0.707
Show solution
Solution
The power factor (PF) is given by cos(θ). For a phase angle of 60 degrees, PF = cos(60°) = 0.5.
Correct Answer:
B
— 0.866
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Q. What is the RMS value of an AC voltage given by V(t) = V0 sin(ωt)?
A.
V0
B.
V0/√2
C.
V0√2
D.
0
Show solution
Solution
The RMS value of an AC voltage is given by V_rms = V0/√2.
Correct Answer:
B
— V0/√2
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Q. What is the root mean square (RMS) value of an alternating current (AC) if its peak value is 10 A?
A.
5 A
B.
7.07 A
C.
10 A
D.
14.14 A
Show solution
Solution
The RMS value of an AC is given by I_rms = I_peak / √2. Therefore, I_rms = 10 A / √2 = 7.07 A.
Correct Answer:
B
— 7.07 A
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Q. What is the root mean square (RMS) value of an alternating current (AC) that has a peak value of 10 A?
A.
5 A
B.
7.07 A
C.
10 A
D.
14.14 A
Show solution
Solution
The RMS value of an AC is given by I_rms = I_peak / √2. Therefore, I_rms = 10 A / √2 = 7.07 A.
Correct Answer:
B
— 7.07 A
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Q. What is the total energy stored in an inductor with inductance L carrying a current I?
A.
LI^2
B.
0.5LI^2
C.
I^2/L
D.
0.5I^2/L
Show solution
Solution
The energy stored in an inductor is given by U = 0.5LI^2.
Correct Answer:
B
— 0.5LI^2
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Q. What is the unit of impedance in an AC circuit?
A.
Ohm
B.
Farad
C.
Henry
D.
Coulomb
Show solution
Solution
The unit of impedance in an AC circuit is Ohm, which is the same as resistance.
Correct Answer:
A
— Ohm
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Q. What is the unit of inductance?
A.
Ohm
B.
Henry
C.
Farad
D.
Coulomb
Show solution
Solution
The unit of inductance is Henry (H).
Correct Answer:
B
— Henry
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Showing 31 to 58 of 58 (2 Pages)
Alternating Current MCQ & Objective Questions
Understanding Alternating Current (AC) is crucial for students preparing for school and competitive exams. This topic not only forms a significant part of the physics curriculum but also features prominently in various objective questions and MCQs. Practicing Alternating Current MCQ questions helps students enhance their concept clarity and boosts their confidence, leading to better exam performance.
What You Will Practise Here
Definition and characteristics of Alternating Current
Comparison between Alternating Current and Direct Current
Key formulas related to AC, including RMS and peak values
Phase difference and its significance in AC circuits
Diagrams illustrating AC waveforms and their properties
Applications of Alternating Current in daily life
Important questions on AC circuit analysis and impedance
Exam Relevance
The topic of Alternating Current is frequently tested in CBSE, State Boards, NEET, and JEE exams. Students can expect questions that assess their understanding of AC theory, calculations involving AC circuits, and real-world applications. Common question patterns include numerical problems, conceptual questions, and diagram-based queries, making it essential to practice thoroughly.
Common Mistakes Students Make
Confusing RMS value with peak value in AC calculations
Misunderstanding the phase relationship between voltage and current
Overlooking the significance of frequency in AC circuits
Neglecting to apply the correct formulas during problem-solving
FAQs
Question: What is the difference between AC and DC?Answer: Alternating Current (AC) changes direction periodically, while Direct Current (DC) flows in one direction only.
Question: How is the RMS value of AC calculated?Answer: The RMS value of an AC waveform is calculated by taking the square root of the average of the squares of the instantaneous values over one complete cycle.
Now is the time to strengthen your understanding of Alternating Current. Dive into our practice MCQs and test your knowledge to excel in your exams!
