Circuit Theory MCQ & Objective Questions
Circuit Theory is a fundamental topic in electrical engineering and physics that plays a crucial role in various school and competitive exams. Mastering this subject not only enhances your understanding of electrical circuits but also boosts your exam scores. Practicing MCQs and objective questions helps you identify important concepts and improves your problem-solving skills, making it easier to tackle exam preparation effectively.
What You Will Practise Here
Basic concepts of circuit elements: resistors, capacitors, and inductors
Ohm's Law and its applications in circuit analysis
Series and parallel circuits: calculations and characteristics
KVL (Kirchhoff's Voltage Law) and KCL (Kirchhoff's Current Law)
Thevenin's and Norton's Theorems for circuit simplification
AC and DC circuit analysis techniques
Power calculations in electrical circuits
Exam Relevance
Circuit Theory is a significant topic in various examinations, including CBSE, State Boards, NEET, and JEE. Students can expect questions that test their understanding of circuit components, laws, and theorems. Common question patterns include numerical problems, conceptual MCQs, and application-based scenarios that require a solid grasp of the subject. Familiarity with these patterns can greatly enhance your performance in exams.
Common Mistakes Students Make
Confusing series and parallel circuit calculations
Misapplying Ohm's Law in complex circuits
Overlooking the significance of units in calculations
Neglecting to apply Kirchhoff's Laws correctly
Failing to simplify circuits using Thevenin's and Norton's Theorems
FAQs
Question: What are the key formulas I should remember for Circuit Theory?Answer: Important formulas include Ohm's Law (V = IR), power formulas (P = VI), and the rules for series and parallel resistances.
Question: How can I improve my Circuit Theory problem-solving skills?Answer: Regular practice of Circuit Theory MCQ questions and understanding the underlying concepts will significantly enhance your skills.
Start solving practice MCQs today to solidify your understanding of Circuit Theory and prepare effectively for your exams. Remember, consistent practice is the key to success!
Q. In a series AC circuit, how does the total impedance (Z) relate to resistance (R) and reactance (X)?
A.
Z = R + X
B.
Z = R - X
C.
Z = √(R^2 + X^2)
D.
Z = R * X
Show solution
Solution
The total impedance in a series AC circuit is calculated using the formula Z = √(R^2 + X^2), where R is resistance and X is reactance.
Correct Answer:
C
— Z = √(R^2 + X^2)
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Q. In a series AC circuit, if the voltage is 120V and the current is 10A, what is the power consumed?
A.
120W
B.
100W
C.
1000W
D.
1200W
Show solution
Solution
Power (P) in an AC circuit is calculated as P = V * I. Therefore, P = 120V * 10A = 1200W.
Correct Answer:
D
— 1200W
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Q. In a series circuit with a 12V battery and two resistors of 4Ω and 6Ω, what is the current flowing through the circuit?
A.
0.8 A
B.
1.2 A
C.
2 A
D.
3 A
Show solution
Solution
Total resistance R = 4Ω + 6Ω = 10Ω. Using Ohm's Law, I = V / R = 12V / 10Ω = 1.2 A.
Correct Answer:
B
— 1.2 A
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Q. In a series circuit with a 24V source and two resistors of 4Ω and 8Ω, what is the voltage across the 8Ω resistor?
A.
16V
B.
8V
C.
12V
D.
4V
Show solution
Solution
Using voltage division, V8Ω = Vtotal * (R8Ω / (R4Ω + R8Ω)) = 24V * (8Ω / (4Ω + 8Ω)) = 24V * (8/12) = 16V.
Correct Answer:
A
— 16V
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Q. In a series circuit with a 9V battery and two resistors (3Ω and 6Ω), what is the current flowing through the circuit?
Show solution
Solution
Total resistance R = 3Ω + 6Ω = 9Ω; I = V / R = 9V / 9Ω = 1A.
Correct Answer:
B
— 2A
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Q. In a series circuit with a 9V battery and two resistors (3Ω and 6Ω), what is the voltage across the 6Ω resistor?
A.
6V
B.
3V
C.
9V
D.
4.5V
Show solution
Solution
Using voltage division, V = V_total * (R / (R1 + R2)) = 9V * (6Ω / (3Ω + 6Ω)) = 6V.
Correct Answer:
A
— 6V
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Q. In a series circuit, how does the total current relate to the individual branch currents according to KCL?
A.
Total current is the sum of branch currents
B.
Total current is the average of branch currents
C.
Total current is the maximum branch current
D.
Total current is the minimum branch current
Show solution
Solution
According to Kirchhoff's Current Law (KCL), the total current entering a junction is equal to the total current leaving the junction, which means the total current is the sum of the branch currents.
Correct Answer:
A
— Total current is the sum of branch currents
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Q. In a series circuit, if one resistor fails open, what happens to the current?
A.
It increases
B.
It decreases
C.
It becomes zero
D.
It remains the same
Show solution
Solution
In a series circuit, if one resistor fails open, the entire circuit is interrupted, and the current becomes zero.
Correct Answer:
C
— It becomes zero
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Q. In a series circuit, if the total voltage is 12V and the resistance is 4Ω, what is the current flowing through the circuit?
A.
3A
B.
4A
C.
12A
D.
0.33A
Show solution
Solution
Using Ohm's Law, I = V / R = 12V / 4Ω = 3A.
Correct Answer:
A
— 3A
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Q. In a series circuit, if the total voltage is 12V and the resistances are 2Ω and 4Ω, what is the current flowing through the circuit?
Show solution
Solution
Using Ohm's Law, the total resistance is 2Ω + 4Ω = 6Ω. The current I = V / R = 12V / 6Ω = 2A.
Correct Answer:
B
— 3A
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Q. In a series circuit, if the total voltage is 12V and the resistances are 2Ω, 3Ω, and 5Ω, what is the current flowing through the circuit?
Show solution
Solution
Total resistance R = 2 + 3 + 5 = 10Ω. Using Ohm's Law, I = V / R = 12V / 10Ω = 1.2A.
Correct Answer:
B
— 2A
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Q. In a series RLC circuit, if the resistance is 10Ω, the inductance is 0.1H, and the capacitance is 100μF, what is the resonant frequency?
A.
159.15Hz
B.
100Hz
C.
50Hz
D.
200Hz
Show solution
Solution
The resonant frequency (f0) is given by f0 = 1 / (2π√(LC)). Here, L = 0.1H and C = 100μF, so f0 = 1 / (2π√(0.1 * 0.0001)) = 159.15Hz.
Correct Answer:
A
— 159.15Hz
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Q. In an AC circuit, if the impedance is 5Ω and the current is 2A, what is the voltage across the circuit?
A.
10V
B.
5V
C.
2.5V
D.
1V
Show solution
Solution
Using Ohm's Law for AC, V = I * Z = 2A * 5Ω = 10V.
Correct Answer:
A
— 10V
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Q. In an AC circuit, if the voltage is given as V(t) = 100√2 sin(ωt), what is the RMS voltage?
A.
100 V
B.
70.71 V
C.
141.42 V
D.
50 V
Show solution
Solution
The RMS voltage (V_rms) for a sinusoidal waveform is V_peak / √2, so V_rms = 100√2 / √2 = 100 V.
Correct Answer:
B
— 70.71 V
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Q. In an AC circuit, if the voltage is given as V(t) = 10sin(100t), what is the peak voltage?
A.
10V
B.
5V
C.
7.07V
D.
0V
Show solution
Solution
The peak voltage (V_peak) is the coefficient of the sine function, which is 10V.
Correct Answer:
A
— 10V
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Q. In an AC circuit, what does impedance represent?
A.
The total opposition to current flow
B.
The total voltage in the circuit
C.
The total power consumed
D.
The total current flowing
Show solution
Solution
Impedance in an AC circuit represents the total opposition to current flow, combining resistance and reactance.
Correct Answer:
A
— The total opposition to current flow
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Q. In an AC circuit, what does the impedance (Z) represent?
A.
Total opposition to current flow
B.
Only resistance
C.
Only reactance
D.
Voltage drop
Show solution
Solution
Impedance (Z) is the total opposition that a circuit offers to the flow of alternating current, combining both resistance and reactance.
Correct Answer:
A
— Total opposition to current flow
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Q. In an AC circuit, what does the term 'impedance' refer to?
A.
Resistance only
B.
Total opposition to current
C.
Voltage drop
D.
Current flow
Show solution
Solution
Impedance is the total opposition that a circuit offers to the flow of alternating current, which includes both resistance and reactance.
Correct Answer:
B
— Total opposition to current
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Q. In an AC circuit, what is the impedance of a circuit with a resistor of 4Ω and an inductor with a reactance of 3Ω?
Show solution
Solution
Impedance (Z) in a series circuit is calculated using Z = √(R^2 + X_L^2). Here, Z = √(4^2 + 3^2) = √(16 + 9) = √25 = 5Ω.
Correct Answer:
B
— 7Ω
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Q. In an AC circuit, what is the impedance of a circuit with a resistor of 5Ω and an inductor with a reactance of 3Ω?
Show solution
Solution
Impedance Z = √(R^2 + X_L^2) = √(5^2 + 3^2) = √(25 + 9) = √34 ≈ 8Ω.
Correct Answer:
B
— 8Ω
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Q. In an AC circuit, what is the phase difference between voltage and current in a purely resistive circuit?
A.
0 degrees
B.
90 degrees
C.
180 degrees
D.
270 degrees
Show solution
Solution
In a purely resistive circuit, the voltage and current are in phase, resulting in a phase difference of 0 degrees.
Correct Answer:
A
— 0 degrees
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Q. In an AC circuit, what is the phase difference between voltage and current in a purely resistive load?
A.
0 degrees
B.
90 degrees
C.
180 degrees
D.
270 degrees
Show solution
Solution
In a purely resistive load, the voltage and current are in phase, meaning the phase difference is 0 degrees.
Correct Answer:
A
— 0 degrees
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Q. In an AC circuit, what is the power factor?
A.
Ratio of real power to apparent power
B.
Ratio of reactive power to real power
C.
Total power consumed
D.
Voltage divided by current
Show solution
Solution
The power factor in an AC circuit is defined as the ratio of real power (P) to apparent power (S), indicating how effectively the current is being converted into useful work.
Correct Answer:
A
— Ratio of real power to apparent power
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Q. Using KCL, if three currents enter a node: 5A, 3A, and 2A, what is the current leaving the node?
Show solution
Solution
According to KCL, Iin = Iout; 5A + 3A + 2A = Iout; Iout = 10A.
Correct Answer:
D
— 10A
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Q. Using KCL, if three currents entering a node are 2A, 3A, and 1A, what is the current leaving the node?
Show solution
Solution
According to KCL, the sum of currents entering a node equals the sum of currents leaving. Therefore, Iout = 2A + 3A + 1A = 6A.
Correct Answer:
B
— 4A
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Q. Using KCL, if three currents entering a node are 5A, 3A, and 2A, what is the total current leaving the node?
Show solution
Solution
According to KCL, total current entering = total current leaving. 5A + 3A + 2A = 10A leaving.
Correct Answer:
B
— 8A
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Q. What does KCL state about currents at a junction?
A.
The sum of currents entering equals the sum of currents leaving
B.
The sum of voltages equals zero
C.
Current is constant in a closed loop
D.
Power is conserved in a circuit
Show solution
Solution
Kirchhoff's Current Law (KCL) states that the total current entering a junction must equal the total current leaving that junction.
Correct Answer:
A
— The sum of currents entering equals the sum of currents leaving
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Q. What does Kirchhoff's Voltage Law (KVL) state?
A.
The sum of currents in a closed loop is zero
B.
The sum of voltages in a closed loop is zero
C.
The total power in a circuit is constant
D.
The total resistance in a circuit is constant
Show solution
Solution
KVL states that the sum of the electrical potential differences (voltages) around any closed network is zero.
Correct Answer:
B
— The sum of voltages in a closed loop is zero
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Q. What does KVL (Kirchhoff's Voltage Law) state?
A.
The sum of currents in a loop is zero
B.
The sum of voltages in a closed loop is zero
C.
The voltage across a resistor is constant
D.
The total power in a circuit is zero
Show solution
Solution
KVL states that the sum of the electrical potential differences (voltages) around any closed network is zero.
Correct Answer:
B
— The sum of voltages in a closed loop is zero
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Q. What does KVL state about the voltages in a closed loop?
A.
The sum of voltages is zero
B.
The sum of currents is zero
C.
The sum of resistances is zero
D.
The sum of powers is zero
Show solution
Solution
Kirchhoff's Voltage Law (KVL) states that the sum of the electrical potential differences (voltages) around any closed network is zero.
Correct Answer:
A
— The sum of voltages is zero
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