Q. A capacitor of 10μF is connected to an AC source of frequency 50Hz. What is the capacitive reactance? (2022)
A.
318.3Ω
B.
159.15Ω
C.
31.83Ω
D.
6.36Ω
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Solution
Capacitive reactance XC = 1/(2πfC) = 1/(2π*50*10e-6) ≈ 318.3Ω.
Correct Answer:
B
— 159.15Ω
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Q. A capacitor of 10μF is connected to an AC source of frequency 60Hz. What is the capacitive reactance? (2020)
A.
26.3Ω
B.
16.7Ω
C.
10.5Ω
D.
5.3Ω
Show solution
Solution
Capacitive reactance Xc = 1/(ωC) where ω = 2πf. Calculate Xc.
Correct Answer:
A
— 26.3Ω
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Q. A capacitor of capacitance C is connected to an AC source of frequency f. What is the capacitive reactance? (2020)
A.
1/(2πfC)
B.
2πfC
C.
C/(2πf)
D.
2πf
Show solution
Solution
The capacitive reactance is given by XC = 1/(2πfC).
Correct Answer:
A
— 1/(2πfC)
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Q. A circuit has a resistance of 10 Ω and a reactance of 10 Ω. What is the impedance of the circuit? (2020)
A.
10 Ω
B.
14.14 Ω
C.
20 Ω
D.
5 Ω
Show solution
Solution
The impedance Z = √(R² + X²) = √(10² + 10²) = √200 = 14.14 Ω.
Correct Answer:
B
— 14.14 Ω
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Q. A circuit has a resistance of 10Ω and a reactance of 5Ω. What is the impedance of the circuit? (2021)
A.
5Ω
B.
10Ω
C.
√125Ω
D.
√(10² + 5²)Ω
Show solution
Solution
The impedance Z is calculated as Z = √(R² + X²) = √(10² + 5²) = √125Ω.
Correct Answer:
D
— √(10² + 5²)Ω
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Q. A circuit has a resistance of 10Ω and a reactance of 5Ω. What is the impedance? (2020)
A.
5Ω
B.
10Ω
C.
√125Ω
D.
√(10² + 5²)Ω
Show solution
Solution
The impedance Z = √(R² + X²) = √(10² + 5²) = √125Ω.
Correct Answer:
D
— √(10² + 5²)Ω
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Q. A coil has an inductance of 0.5 H and is connected to a 50 Hz AC supply. What is the inductive reactance? (2020)
A.
25.13 Ω
B.
31.42 Ω
C.
50 Ω
D.
100 Ω
Show solution
Solution
Inductive reactance Xl = 2πfL = 2π(50)(0.5) = 31.42 Ω.
Correct Answer:
B
— 31.42 Ω
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Q. A resistor of 10 Ω and a capacitor of 100 μF are connected in series to an AC source of frequency 50 Hz. What is the capacitive reactance? (2020)
A.
3.18 Ω
B.
31.8 Ω
C.
0.318 Ω
D.
318 Ω
Show solution
Solution
Capacitive reactance Xc = 1/(2πfC) = 1/(2π(50)(100 × 10^-6)) ≈ 3.18 Ω.
Correct Answer:
A
— 3.18 Ω
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Q. If a capacitor is charged to 12V and has a capacitance of 6μF, what is the stored energy? (2022)
A.
0.432 mJ
B.
0.072 mJ
C.
0.864 mJ
D.
0.216 mJ
Show solution
Solution
Energy = 0.5 × C × V² = 0.5 × 6 × 10^-6 × 12² = 0.432 mJ.
Correct Answer:
A
— 0.432 mJ
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Q. If the capacitance in an AC circuit is increased, what happens to the capacitive reactance? (2023)
A.
It increases
B.
It decreases
C.
It remains the same
D.
It becomes zero
Show solution
Solution
Capacitive reactance XC = 1/(ωC). If capacitance C increases, XC decreases.
Correct Answer:
B
— It decreases
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Q. If the current in an AC circuit is given by I(t) = I0 cos(ωt), what is the RMS current? (2023)
A.
I0/√2
B.
I0
C.
2I0
D.
I0/2
Show solution
Solution
RMS current I_rms = I0/√2 for a cosine function.
Correct Answer:
A
— I0/√2
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Q. If the current in an AC circuit is I(t) = 5√2 sin(100t + π/4), what is the RMS current? (2021)
A.
5 A
B.
2.5 A
C.
7.07 A
D.
3.54 A
Show solution
Solution
The RMS current is I_rms = I_peak / √2 = 5√2 / √2 = 5 A.
Correct Answer:
B
— 2.5 A
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Q. If the frequency of an AC source is doubled, how does the inductive reactance change? (2020)
A.
Doubles
B.
Halves
C.
Remains the same
D.
Quadruples
Show solution
Solution
Xl = 2πfL; if f is doubled, Xl also doubles.
Correct Answer:
B
— Halves
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Q. If the frequency of an AC source is doubled, what happens to the inductive reactance of an inductor? (2021)
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
Show solution
Solution
Inductive reactance Xl = ωL, so if frequency is doubled, Xl halves.
Correct Answer:
B
— It halves
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Q. If the frequency of an AC source is doubled, what happens to the inductive reactance? (2014)
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
Show solution
Solution
Inductive reactance XL = 2πfL, so if frequency f is doubled, XL halves.
Correct Answer:
B
— It halves
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Q. If the frequency of an AC source is doubled, what happens to the reactance of a capacitor? (2023)
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
Show solution
Solution
The capacitive reactance Xc = 1/(2πfC) halves when the frequency f is doubled.
Correct Answer:
B
— It halves
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Q. If the frequency of an AC source is doubled, what happens to the reactance of an inductor? (2023)
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
Show solution
Solution
The reactance of an inductor is given by XL = ωL. If frequency is doubled, reactance also doubles.
Correct Answer:
A
— It doubles
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Q. If the inductance of a coil is 0.5H and the frequency is 60Hz, what is the inductive reactance? (2023)
A.
31.42 ohms
B.
18.85 ohms
C.
37.70 ohms
D.
25.13 ohms
Show solution
Solution
Xl = 2πfL = 2π × 60 × 0.5 = 31.42 ohms.
Correct Answer:
A
— 31.42 ohms
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Q. If the inductive reactance of a coil is 30Ω and the resistance is 10Ω, what is the total impedance? (2018)
A.
10Ω
B.
30Ω
C.
33.33Ω
D.
40Ω
Show solution
Solution
Total impedance Z = √(R² + (XL)²) = √(10² + 30²) = √(100 + 900) = √1000 = 31.62Ω.
Correct Answer:
C
— 33.33Ω
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Q. If the power factor of an AC circuit is 0.8, what is the angle between the current and voltage? (2021)
A.
36.87°
B.
53.13°
C.
60°
D.
45°
Show solution
Solution
The angle θ can be found using cos(θ) = power factor. Thus, θ = cos⁻¹(0.8) ≈ 36.87°.
Correct Answer:
B
— 53.13°
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Q. If the total current in an AC circuit is 5A and the voltage is 120V, what is the impedance? (2023)
A.
24Ω
B.
20Ω
C.
30Ω
D.
15Ω
Show solution
Solution
Impedance (Z) = Voltage (V) / Current (I) = 120V / 5A = 24Ω.
Correct Answer:
B
— 20Ω
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Q. If the total impedance in an AC circuit is 20Ω and the current is 2A, what is the voltage across the circuit? (2023)
A.
10V
B.
20V
C.
30V
D.
40V
Show solution
Solution
Using Ohm's law, V = IZ = 2A * 20Ω = 40V.
Correct Answer:
B
— 20V
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Q. If the voltage across a capacitor in an AC circuit is 100 V and the capacitive reactance is 50 ohms, what is the current through the capacitor? (2021)
A.
2 A
B.
1 A
C.
0.5 A
D.
0.25 A
Show solution
Solution
Current I = V/Xc = 100 V / 50 ohms = 2 A.
Correct Answer:
B
— 1 A
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Q. If the voltage across a capacitor in an AC circuit is 100 V and the capacitive reactance is 50 ohms, what is the current? (2020)
A.
2 A
B.
0.5 A
C.
5 A
D.
10 A
Show solution
Solution
Using Ohm's law, I = V/Xc = 100 V / 50 ohms = 2 A.
Correct Answer:
B
— 0.5 A
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Q. If the voltage across a capacitor in an AC circuit is 100 V and the capacitive reactance is 50 Ω, what is the current through the capacitor? (2021)
A.
2 A
B.
0.5 A
C.
5 A
D.
10 A
Show solution
Solution
Using Ohm's law, I = V/Xc = 100 V / 50 Ω = 2 A.
Correct Answer:
B
— 0.5 A
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Q. If the voltage across a capacitor in an AC circuit is 100V and the capacitive reactance is 50 ohms, what is the current? (2023)
A.
2A
B.
0.5A
C.
5A
D.
10A
Show solution
Solution
Using Ohm's law, I = V/Xc = 100V/50Ω = 2A.
Correct Answer:
A
— 2A
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Q. If the voltage across a capacitor in an AC circuit is 100V and the capacitive reactance is 50Ω, what is the current through the capacitor? (2023)
Show solution
Solution
Current (I) = Voltage (V) / Capacitive Reactance (XC) = 100V / 50Ω = 2A.
Correct Answer:
B
— 2A
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Q. If the voltage across a capacitor in an AC circuit is 100V and the capacitive reactance is 50Ω, what is the current? (2021)
A.
2A
B.
0.5A
C.
5A
D.
100A
Show solution
Solution
Using Ohm's law, I = V/Xc = 100V/50Ω = 2A.
Correct Answer:
B
— 0.5A
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Q. If the voltage across a capacitor is 100V and the capacitive reactance is 50 ohms, what is the current through the capacitor? (2022)
A.
2 A
B.
1 A
C.
0.5 A
D.
0.25 A
Show solution
Solution
I = V/Xc = 100/50 = 2 A.
Correct Answer:
B
— 1 A
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Q. If the voltage across a resistor is 240V and the resistance is 60 ohms, what is the current flowing through it? (2020)
Show solution
Solution
I = V / R = 240V / 60Ω = 4A.
Correct Answer:
C
— 6A
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Showing 1 to 30 of 122 (5 Pages)
AC Circuits MCQ & Objective Questions
Understanding AC Circuits is crucial for students preparing for school exams and competitive tests in India. Mastering this topic not only enhances your conceptual clarity but also boosts your confidence in tackling objective questions. Practicing AC Circuits MCQs and important questions will significantly improve your exam performance and help you score better.
What You Will Practise Here
Fundamental concepts of alternating current (AC) and its characteristics
Key formulas related to AC circuits, including impedance and reactance
Phase difference and its impact on AC circuit behavior
Resonance in AC circuits and its applications
AC circuit analysis techniques, including series and parallel circuits
Diagrams illustrating AC waveforms and circuit configurations
Real-world applications of AC circuits in electrical engineering
Exam Relevance
AC Circuits is a vital topic in various examinations, including CBSE, State Boards, NEET, and JEE. Questions related to AC Circuits often appear in both theoretical and practical formats. Students can expect to encounter problems involving calculations of current, voltage, and power in AC circuits, as well as conceptual questions that test their understanding of waveforms and circuit behavior. Familiarity with common question patterns will aid in effective exam preparation.
Common Mistakes Students Make
Confusing AC with DC concepts, leading to incorrect application of formulas
Misunderstanding phase relationships between voltage and current
Overlooking the significance of reactance in circuit analysis
Failing to accurately interpret circuit diagrams
Neglecting the practical applications of AC circuits in real-life scenarios
FAQs
Question: What are the key differences between AC and DC circuits?Answer: AC circuits involve alternating current that changes direction periodically, while DC circuits involve direct current that flows in one direction.
Question: How can I improve my understanding of AC Circuits for exams?Answer: Regular practice of AC Circuits MCQ questions and reviewing important concepts will enhance your understanding and retention.
Now is the time to take charge of your learning! Dive into our practice MCQs on AC Circuits and test your understanding. The more you practice, the better prepared you will be for your exams!
