**A.C. Fundamentals, Circuits, and Circuit Theory**

AC fundamentals, circuits, and circuit theory are fundamental concepts in electrical engineering and form the basis for understanding and analyzing electrical circuits.

**1. ****AC Fundamentals:**

· **AC (alternating current)**: AC is an electrical current that periodically changes its direction and magnitude. It is commonly used for power transmission and distribution.

· **Period and frequency: **The period of an AC waveform is the time taken for one complete cycle, while the frequency is the number of cycles per second.

· **Amplitude:** The peak value of an AC waveform is called its amplitude. It represents the maximum magnitude of the current or voltage.

· ** RMS value: **The root mean square (RMS) value of an AC waveform is a measure of its effective value and is used for calculations. For a sinusoidal waveform, the RMS value is equal to the peak value divided by the square root of 2.

**2. ****Circuits:**

· **Electrical circuit:** An electrical circuit is a closed path that allows the flow of electric current. It consists of various components such as resistors, capacitors, inductors, and sources of electrical energy (e.g., voltage sources).

· **Circuit elements: **There are three basic circuit elements: resistors (which resist the flow of current), capacitors (which store electrical energy in the form of charge), and inductors (which store energy in the form of a magnetic field).

· **Kirchhoff’s laws:** Kirchhoff’s laws are fundamental principles used to analyze electrical circuits. They include Kirchhoff’s current law (KCL), which states that the sum of currents entering a node is equal to the sum of currents leaving the node, and Kirchhoff’s voltage law (KVL), which states that the sum of voltages around any closed loop in a circuit is zero.

**3. ****Circuit Theory:**

· **Network analysis: **Circuit theory involves analyzing electrical circuits using mathematical techniques. Network analysis techniques, such as nodal analysis and mesh analysis, are used to determine voltage and current relationships in a circuit.

· **Ohm’s law:** Ohm’s law states that the current flowing through a conductor is directly proportional to the voltage across it and inversely proportional to its resistance.

· ** Impedance:** Impedance is the general term used to describe the opposition to the flow of AC current in a circuit. It takes into account both resistance and reactance (which is related to capacitance and inductance) and is represented by the symbol Z.

· ** AC circuit analysis:** AC circuit analysis involves analyzing circuits with AC voltage or current sources. Techniques such as phasor analysis, impedance matching, and resonance are used to determine the behavior of AC circuits.

Understanding AC fundamentals, circuits, and circuit theory is crucial for designing and analyzing electrical systems, from basic electronic circuits to complex power distribution networks. These concepts form the foundation for more advanced topics in electrical engineering.

## Circuit Theory MCQ with Answers pdf | AC Circuit Questions and Answers pdf

**1. Which of the following is an example of an AC power source?**

a) Battery

b) Solar panel

c) Generator

d) Thermocouple

**Answer: c) Generator**

**2. What is the unit of frequency?**

a) Volts

b) Amperes

c) Hertz

d) Ohms

**Answer: c) Hertz**

**3. What is the time period of a waveform with a frequency of 50 Hz?**

a) 0.02 seconds

b) 0.05 seconds

c) 0.2 seconds

d) 2 seconds

**Answer: b) 0.05 seconds**

**4. Which circuit element stores energy in a magnetic field?**

a) Resistor

b) Capacitor

c) Inductor

d) Transistor

**Answer: c) Inductor**

**5. Kirchhoff’s voltage law is based on the principle of conservation of:**

a) Charge

b) Energy

c) Power

d) Momentum

**Answer: b) Energy**

**6. What is the formula for calculating the power dissipated in a resistor?**

a) P = V × I

b) P = V / I

c) P = I / V

d) P = I^2 × R

**Answer: d) P = I^2 × R**

**7. What is the unit of impedance?**

a) Volts

b) Amperes

c) Ohms

d) Farads

**Answer: c) Ohms**

**8. Which circuit analysis technique is based on the application of Kirchhoff’s current law?**

a) Nodal analysis

b) Mesh analysis

c) Superposition analysis

d) Thevenin’s theorem

**Answer: a) Nodal analysis**

**9. The reactive power in an AC circuit is measured in:**

a) Watts

b) Volt-amperes

c) Amperes

d) Farads

**Answer: b) Volt-amperes**

**10. What is the resonance frequency of an RLC circuit with an inductance of 10 mH and a capacitance of 100 μF?**

a) 1 Hz

b) 10 Hz

c) 100 Hz

d) 1 kHz

**Answer: a) 1 Hz**

## ac circuit mcq questions and answers | circuit theory questions and answers pdf

**11. What is the phase difference between the voltage and current in a purely resistive circuit?**

a) 0 degrees

b) 45 degrees

c) 90 degrees

d) 180 degrees

**Answer: a) 0 degrees**

**12. Which circuit element opposes the change in current and stores energy in a magnetic field?**

a) Resistor

b) Capacitor

c) Inductor

d) Transformer

**Answer: c) Inductor**

**13. Which of the following is used to convert AC voltage to a different level?**

a) Diode

b) Transistor

c) Capacitor

d) Transformer

**Answer: d) Transformer**

**14. Which law states that the algebraic sum of voltage drops around any closed loop in a circuit is zero?**

a) Kirchhoff’s voltage law (KVL)

b) Ohm’s law

c) Kirchhoff’s current law (KCL)

d) Faraday’s law

**Answer: a) Kirchhoff’s voltage law (KVL)**

**15. What is the reactance of a purely capacitive circuit?**

a) Positive

b) Negative

c) Zero

d) Infinite

**Answer: d) Infinite**

**16. What is the power factor of a circuit with a purely resistive load?**

a) 0

b) 0.5

c) 1

d) It cannot be determined without additional information

**Answer: c) 1**

**17. Which circuit analysis technique involves replacing a complex network with an equivalent voltage source and series impedance?**

a) Nodal analysis

b) Mesh analysis

c) Superposition analysis

d) Thevenin’s theorem

**Answer: d) Thevenin’s theorem**

**18. What is the unit of apparent power?**

a) Volts

b) Amperes

c) Watts

d) Volt-amperes

**Answer: d) Volt-amperes**

**19. Which factor affects the reactance of an inductor?**

a) Frequency

b) Voltage

c) Resistance

d) Power

**Answer: a) Frequency**

**20. What is the condition for maximum power transfer from a source to a load in an AC circuit?**

a) The load impedance should be zero.

b) The source impedance should be zero.

c) The load impedance should be complex.

d) The source impedance should be equal to the complex conjugate of the load impedance.

**Answer: d) The source impedance should be equal to the complex conjugate of the load impedance.**

## electrical circuit theory questions and answers pdf | ac theory questions and answers pdf

**21. What is the relationship between frequency and wavelength of an AC waveform traveling in a medium?**

a) They are directly proportional.

b) They are inversely proportional.

c) They are unrelated.

d) They have a quadratic relationship.

**Answer: b) They are inversely proportional.**

**22. What is the power factor angle in an AC circuit with a lagging power factor?**

a) 0 degrees

b) 45 degrees

c) 90 degrees

d) 180 degrees

**Answer: c) 90 degrees**

**23. What is the effect of adding a capacitor in parallel to a circuit?**

a) Increases impedance

b) Decreases impedance

c) Increases power factor

d) Decreases power factor

**Answer: b) Decreases impedance**

**24. Which type of circuit consists of only two elements connected in series or parallel?**

a) Series circuit

b) Parallel circuit

c) Combination circuit

d) Complex circuit

**Answer: c) Combination circuit**

**25. Which circuit analysis technique is based on the principle of superposition?**

a) Nodal analysis

b) Mesh analysis

c) Superposition analysis

d) Thevenin’s theorem

**Answer: c) Superposition analysis**

**26. What is the unit of apparent power in an AC circuit?**

a) Volts

b) Amperes

c) Watts

d) Volt-amperes

**Answer: d) Volt-amperes**

**27. What is the reactance of a purely resistive circuit?**

a) Positive

b) Negative

c) Zero

d) Infinite

**Answer: c) Zero**

**28. Which law states that the sum of currents entering a node is equal to the sum of currents leaving the node?**

a) Kirchhoff’s voltage law (KVL)

b) Ohm’s law

c) Kirchhoff’s current law (KCL)

d) Faraday’s law

**Answer: c) Kirchhoff’s current law (KCL)**

**29. Which factor affects the reactance of a capacitor?**

a) Frequency

b) Voltage

c) Resistance

d) Power

**Answer: a) Frequency**

**30. What is the condition for maximum power transfer from a source to a load in an AC circuit?**

a) The load impedance should be zero.

b) The source impedance should be zero.

c) The load impedance should be complex conjugate of the source impedance.

d) The source impedance should be equal to the load impedance.

**Answer: c) The load impedance should be complex conjugate of the source impedance.**

## circuit theory problems with answers pdf | circuit theory gate questions with solutions pdf

**31. What is the relationship between reactance and frequency in an inductive circuit?**

a) Directly proportional

b) Inversely proportional

c) No relationship

d) Quadratically proportional

**Answer: a) Directly proportional**

**32. What is the power factor of a circuit with a leading power factor?**

a) 0

b) 0.5

c) 1

d) It cannot be determined without additional information

**Answer: c) 1**

**33. Which circuit element stores energy in both an electric field and a magnetic field?**

a) Resistor

b) Capacitor

c) Inductor

d) Diode

**Answer: b) Capacitor**

**34. Which law states that the algebraic sum of currents at any node in a circuit is zero?**

a) Kirchhoff’s voltage law (KVL)

b) Ohm’s law

c) Kirchhoff’s current law (KCL)

d) Faraday’s law

**Answer: c) Kirchhoff’s current law (KCL)**

**35. What is the unit of reactance?**

a) Volts

b) Amperes

c) Ohms

d) Farads

**Answer: c) Ohms**

**36. Which circuit analysis technique involves solving a system of equations based on the voltage drops across circuit elements?**

a) Nodal analysis

b) Mesh analysis

c) Superposition analysis

d) Thevenin’s theorem

**Answer: b) Mesh analysis**

**37. What is the unit of complex power?**

a) Volts

b) Amperes

c) Watts

d) Volt-amperes

**Answer: d) Volt-amperes**

**38. Which factor affects the capacitance of a capacitor?**

a) Frequency

b) Voltage

c) Resistance

d) Power

**Answer: b) Voltage**

**39. What is the condition for resonance in an RLC circuit?**

a) Inductive reactance is equal to capacitive reactance

b) Inductive reactance is greater than capacitive reactance

c) Capacitive reactance is greater than inductive reactance

d) No reactive components are present in the circuit

**Answer: a) Inductive reactance is equal to capacitive reactance**

**40. Which theorem states that any linear circuit can be replaced by an equivalent circuit containing a single voltage source and a single impedance?**

a) Norton’s theorem

b) Thevenin’s theorem

c) Superposition theorem

d) Maximum power transfer theorem

**Answer: b) Thevenin’s theorem**

## Circuit theory question bank with answers pdf | Electrical circuit theory questions and answers

**41. What is the relationship between impedance and frequency in a capacitive circuit?**

a) Directly proportional

b) Inversely proportional

c) No relationship

d) Quadratically proportional

**Answer: b) Inversely proportional**

**42. What is the power factor of a purely capacitive circuit?**

a) 0

b) 0.5

c) 1

d) It cannot be determined without additional information

**Answer: a) 0**

**43. Which circuit element can store energy in both an electric field and a** **magnetic field?**

a) Resistor

b) Capacitor

c) Inductor

d) Transformer

**Answer: d) Transformer**

**44. Which law states that the sum of the electromotive forces in any closed loop of a circuit is equal to the sum of the potential drops?**

a) Kirchhoff’s voltage law (KVL)

b) Ohm’s law

c) Kirchhoff’s current law (KCL)

d) Faraday’s law

**Answer: a) Kirchhoff’s voltage law (KVL)**

**45. What is the unit of inductive reactance?**

a) Volts

b) Amperes

c) Ohms

d) Farads

**Answer: c) Ohms**

**46. Which circuit analysis technique involves solving a system of equations based on the current entering or leaving each node?**

a) Nodal analysis

b) Mesh analysis

c) Superposition analysis

d) Thevenin’s theorem

**Answer: a) Nodal analysis**

**47. What is the unit of complex impedance?**

a) Volts

b) Amperes

c) Ohms

d) Farads

**Answer: c) Ohms**

**48. Which factor affects the inductance of an inductor?**

a) Frequency

b) Voltage

c) Resistance

d) Power

**Answer: c) Resistance**

**49. Which theorem states that any linear circuit can be replaced by an equivalent circuit containing a single current source and a single impedance?**

a) Norton’s theorem

b) Thevenin’s theorem

c) Superposition theorem

d) Maximum power transfer theorem

**Answer: a) Norton’s theorem**

**50. What is the condition for maximum power transfer from a source to a load** **in an AC circuit?**

a) The load impedance should be zero.

b) The source impedance should be zero.

c) The load impedance should be complex conjugate of the source impedance.

d) The source impedance should be equal to the load impedance.

**Answer: c) The load impedance should be complex conjugate of the source impedance.**

**51. What is the relationship between power and resistance in an AC circuit?**

a) Directly proportional

b) Inversely proportional

c) No relationship

d) Quadratically proportional

**Answer: a) Directly proportional**

**52. What is the power factor of a circuit with a leading power factor?**

a) 0

b) 0.5

c) 1

d) It cannot be determined without additional information

**Answer: a) 0**

**53. Which circuit element can block the flow of current in one direction but allow it in the opposite direction?**

a) Resistor

b) Capacitor

c) Inductor

d) Diode

**Answer: d) Diode**

**54. Which law states that the induced electromotive force in a circuit is proportional to the rate of change of magnetic flux?**

a) Kirchhoff’s voltage law (KVL)

b) Ohm’s law

c) Kirchhoff’s current law (KCL)

d) Faraday’s law

**Answer: d) Faraday’s law**

**55. What is the unit of capacitive reactance?**

a) Volts

b) Amperes

c) Ohms

d) Farads

**Answer: c) Ohms**

**56. Which circuit analysis technique involves solving a system of equations based on the current loops in the circuit?**

a) Nodal analysis

b) Mesh analysis

c) Superposition analysis

d) Thevenin’s theorem

**Answer: b) Mesh analysis**

**57. What is the unit of complex admittance?**

a) Volts

b) Amperes

c) Siemens

d) Farads

**Answer: c) Siemens**

**58. Which factor affects the capacitance of a capacitor?**

a) Frequency

b) Voltage

c) Resistance

d) Power

**Answer: a) Frequency**

**59. Which theorem states that the current flowing through a load resistance can be calculated by finding the current through a short circuit across the load terminals?**

a) Norton’s theorem

b) Thevenin’s theorem

c) Superposition theorem

d) Maximum power transfer theorem

**Answer: a) Norton’s theorem**

**60. What is the condition for resonance in an RLC circuit?**

a) Inductive reactance is equal to capacitive reactance

b) Inductive reactance is greater than capacitive reactance

c) Capacitive reactance is greater than inductive reactance

d) No reactive components are present in the circuit

**Answer: a) Inductive reactance is equal to capacitive reactance**

**61. What is the relationship between power and voltage in an AC circuit?**

a) Directly proportional

b) Inversely proportional

c) No relationship

d) Quadratically proportional

**Answer: a) Directly proportional**

**62. What is the power factor of a circuit with a lagging power factor?**

a) 0

b) 0.5

c) 1

d) It cannot be determined without additional information

**Answer: c) 1**

**63. Which circuit element is used to store electrical energy in an electric field?**

a) Resistor

b) Capacitor

c) Inductor

d) Transistor

**Answer: b) Capacitor**

**64. Which law states that the sum of the voltage drops across all elements in a closed loop is equal to the sum of the electromotive forces in that loop?**

a) Kirchhoff’s voltage law (KVL)

b) Ohm’s law

c) Kirchhoff’s current law (KCL)

d) Faraday’s law

**Answer: a) Kirchhoff’s voltage law (KVL)**

**65. What is the unit of inductive reactance?**

a) Volts

b) Amperes

c) Ohms

d) Farads

**Answer: c) Ohms**

**66. Which circuit analysis technique involves solving a system of equations based on the voltage and current at each node in the circuit?**

a) Nodal analysis

b) Mesh analysis

c) Superposition analysis

d) Thevenin’s theorem

**Answer: a) Nodal analysis**

**67. What is the unit of complex admittance?**

a) Volts

b) Amperes

c) Siemens

d) Farads

**Answer: c) Siemens**

**68. Which factor affects the inductance of an inductor?**

a) Frequency

b) Voltage

c) Resistance

d) Power

**Answer: c) Resistance**

**69. Which theorem states that any linear bilateral network can be replaced by an equivalent circuit consisting of a single current source and a single parallel impedance?**

a) Norton’s theorem

b) Thevenin’s theorem

c) Superposition theorem

d) Maximum power transfer theorem

**Answer: b) Thevenin’s theorem**

**70. What is the condition for resonance in an RLC circuit?**

a) Inductive reactance is equal to capacitive reactance

b) Inductive reactance is greater than capacitive reactance

c) Capacitive reactance is greater than inductive reactance

d) No reactive components are present in the circuit

**Answer: a) Inductive reactance is equal to capacitive reactance**

**71. What is the relationship between power and current in an AC circuit?**

a) Directly proportional

b) Inversely proportional

c) No relationship

d) Quadratically proportional

**Answer: a) Directly proportional**

**72. What is the power factor of a circuit with a leading power factor?**

a) 0

b) 0.5

c) 1

d) It cannot be determined without additional information

**Answer: a) 0**

**73. Which circuit element is used to store electrical energy in a magnetic field?**

a) Resistor

b) Capacitor

c) Inductor

d) Transformer

**Answer: c) Inductor**

**74. Which law states that the algebraic sum of currents entering and leaving a node is zero?**

a) Kirchhoff’s voltage law (KVL)

b) Ohm’s law

c) Kirchhoff’s current law (KCL)

d) Faraday’s law

**Answer: c) Kirchhoff’s current law (KCL)**

**75. What is the unit of capacitive reactance?**

a) Volts

b) Amperes

c) Ohms

d) Farads

**Answer: c) Ohms**

**76. Which circuit analysis technique involves solving a system of equations based on the current through different loops in the circuit?**

a) Nodal analysis

b) Mesh analysis

c) Superposition analysis

d) Thevenin’s theorem

**Answer: b) Mesh analysis**

**77. What is the unit of complex power?**

a) Volts

b) Amperes

c) Watts

d) Volt-amperes

**Answer: d) Volt-amperes**

**78. Which factor affects the capacitance of a capacitor?**

a) Frequency

b) Voltage

c) Resistance

d) Power

**Answer: b) Voltage**

**79. Which theorem states that any linear network can be replaced by an equivalent circuit consisting of a single current source and a single series** **impedance?**

a) Norton’s theorem

b) Thevenin’s theorem

c) Superposition theorem

d) Maximum power transfer theorem

**Answer: a) Norton’s theorem**

**80. What is the condition for maximum power transfer from a source to a load in an AC circuit?**

a) The load impedance should be zero.

b) The source impedance should be zero.

c) The load impedance should be complex conjugate of the source impedance.

d) The source impedance should be equal to the load impedance.

**Answer: c) The load impedance should be complex conjugate of the source impedance.**

**81. In an AC circuit, what is the phase relationship between voltage and current in an inductive load?**

a) Voltage leads current by 90 degrees

b) Voltage lags current by 90 degrees

c) Voltage and current are in phase

d) There is no phase relationship between voltage and current

**Answer: b) Voltage lags current by 90 degrees**

**82. What is the power factor of a circuit with a lagging power factor?**

a) 0

b) 0.5

c) 1

d) It cannot be determined without additional information

**Answer: a) 0**

**83. Which circuit element allows current to flow in one direction only?**

a) Resistor

b) Capacitor

c) Inductor

d) Diode

**Answer: d) Diode**

**84. What is the unit of resistance?**

a) Volts

b) Amperes

c) Ohms

d) Farads

**Answer: c) Ohms**

**85. Which law states that the algebraic sum of voltage drops in any closed loop of a circuit is zero?**

a) Kirchhoff’s voltage law (KVL)

b) Ohm’s law

c) Kirchhoff’s current law (KCL)

d) Faraday’s law

**Answer: a) Kirchhoff’s voltage law (KVL)**

**86. What is the unit of inductive reactance?**

a) Volts

b) Amperes

c) Ohms

d) Farads

**Answer: c) Ohms**

**87. Which circuit analysis technique involves solving a system of equations based on the voltage and current at each node in the circuit?**

a) Nodal analysis

b) Mesh analysis

c) Superposition analysis

d) Thevenin’s theorem

**Answer: a) Nodal analysis**

**88. What is the unit of complex impedance?**

a) Volts

b) Amperes

c) Ohms

d) Farads

**Answer: c) Ohms**

**89. Which factor affects the capacitance of a capacitor?**

a) Frequency

b) Voltage

c) Resistance

d) Power

**Answer: a) Frequency**