# Basic of Alternating Current MCQs – AC Fundamentals, Circuits, and Circuit TheoryFundamentals of Alternating Current Objective Multiple Choice

Welcome to the Electrical Engineering MCQ blog post on Alternating Current fundamentals, circuits, and circuit theory. This post aims to test your knowledge and understanding of various concepts related to AC circuits in the field of electrical engineering. In this article, we have compiled over 20 multiple-choice questions to challenge your understanding and help you assess your expertise in this subject. Whether you are appearing for a job interview or you are doing an Electrical and Electronics Engineering degree and are preparing for university exams, these objective MCQ Questions with brief explanatory answers are for you. Let’s start

## What does AC stand for in Electrical Engineering

What does AC stand for in electrical engineering

1. Alternating Current
2. Amplitude Control
3. Active Circuit
4. Automatic Control

Correct Option: 1. Alternating Current

Explanation: AC stands for Alternating Current. It is an electric current that periodically changes direction, typically seen in household power outlets and electrical power transmission.

## Which of the following is true about AC circuits

Which of the following is true about AC circuits?

1. The voltage and current are constant over time.
2. The voltage and current vary periodically.
3. The voltage remains constant, but the current varies.
4. The current remains constant, but the voltage varies.

Correct Option: 2. The voltage and current vary periodically.

Explanation: In AC circuits, both voltage and current vary periodically with time. This is in contrast to DC (Direct Current) circuits, where the voltage and current remain constant over time.

## In an AC circuit, the frequency is a measure of

In an AC circuit, the frequency is a measure of:

1. The voltage magnitude
2. The current magnitude
3. The rate of change of voltage
4. The rate at which the direction of current changes

Correct Option: 4. The rate at which the direction of current changes

Explanation: The frequency in an AC circuit refers to the rate at which the direction of current changes per second. It is typically measured in Hertz (Hz).

## Which of the following is true about reactive power

Which of the following is true about reactive power?

1. It represents the power dissipated in a circuit.
2. It is the average power consumed by a circuit.
3. It is the power stored and released by inductive and capacitive elements.
4. It is the instantaneous power at a given point in time.

Correct Option: 3. It is the power stored and released by inductive and capacitive elements.

Explanation: Reactive power is the power stored and released by inductive and capacitive elements in an AC circuit. It is measured in volt-amperes reactive (VAR).

## Which component is used to store electrical energy in an AC circuit

Which component is used to store electrical energy in an AC circuit?

1. Resistor
2. Capacitor
3. Inductor
4. Diode

Correct Option: 2. Capacitor

Explanation: A capacitor is used to store electrical energy in an AC circuit. It consists of two conductive plates separated by an insulating material, allowing it to store and release charge.

## What is the phase difference between voltage and current in a purely resistive AC circuit

What is the phase difference between voltage and current in a purely resistive AC circuit?

1. 0 degrees
2. 90 degrees
3. 180 degrees
4. It depends on the frequency.

Correct Option: 1. 0 degrees

Explanation: In a purely resistive AC circuit, the voltage and current are in phase with each other, meaning there is no phase difference between them. The phase angle is 0 degrees.

## Which of the following is true about the power factor in an AC circuit

Which of the following is true about the power factor in an AC circuit

1. It represents the ratio of real power to apparent power.
2. It represents the ratio of reactive power to apparent power.
3. It is always equal to 1 in an AC circuit.
4. It is independent of the circuit impedance.

Correct Option: 1. It represents the ratio of real power to apparent power.

Explanation: The power factor in an AC circuit is the ratio of real power (the power that performs useful work) to apparent power (the product of voltage and current magnitudes). It indicates the efficiency of power utilization in the circuit.

## Which component is used to block the flow of current in one direction in an AC circuit

Which component is used to block the flow of current in one direction in an AC circuit?

1. Resistor
2. Capacitor
3. Inductor
4. Diode

Correct Option: 4. Diode

Explanation: A diode is a two-terminal electronic component that allows current to flow in only one direction, blocking the flow in the opposite direction. It is often used to rectify AC into DC.

## Which theorem states that the algebraic sum of the potential differences in any closed loop of a network is zero

Which theorem states that the algebraic sum of the potential differences in any closed loop of a network is zero?

1. Kirchhoff’s Current Law
2. Kirchhoff’s Voltage Law
3. Ohm’s Law

Correct Option: 2. Kirchhoff’s Voltage Law

Explanation: Kirchhoff’s Voltage Law (KVL) states that the algebraic sum of the potential differences (voltages) around any closed loop in an electrical network is equal to zero. It is based on the principle of conservation of energy.

## According to the Superposition theorem, in a linear circuit containing multiple independent sources, the total response is obtained by

According to the Superposition theorem, in a linear circuit containing multiple independent sources, the total response is obtained by:

1. Summing the responses due to each source individually.
2. Taking the difference between the responses due to each source individually.
3. Multiplying the responses due to each source individually.
4. Dividing the responses due to each source individually.

Correct Option: 1. Summing the responses due to each source individually.

Explanation: The Superposition theorem states that in a linear circuit containing multiple independent sources, the total response is obtained by summing the responses due to each source individually while keeping other sources turned off (replacing them with their internal resistance).

## Which theorem is used to simplify complex electrical networks into equivalent circuits

Which theorem is used to simplify complex electrical networks into equivalent circuits?

1. Superposition theorem
2. Norton’s theorem
3. Thevenin’s theorem
4. Maximum Power Transfer theorem

Correct Option: 3. Thevenin’s theorem

Explanation: Thevenin’s theorem is used to simplify complex electrical networks by replacing them with an equivalent circuit composed of a Thevenin voltage source and a Thevenin resistance. This simplification allows for easier analysis and calculations.

## In a series RLC circuit, resonance occurs when

In a series RLC circuit, resonance occurs when:

1. The inductive reactance equals the capacitive reactance.
2. The inductive reactance is greater than the capacitive reactance.
3. The inductive reactance is less than the capacitive reactance.
4. The resistance is equal to zero.

Correct Option: 1. The inductive reactance equals the capacitive reactance.

Explanation: In a series RLC circuit, resonance occurs when the inductive reactance (XL) and the capacitive reactance (XC) are equal. At resonance, the circuit impedance is purely resistive, and the current and voltage are in phase.

## Which of the following components is commonly used to step-up or step-down AC voltage levels

Which of the following components is commonly used to step-up or step-down AC voltage levels?

1. Transformer
2. Inductor
3. Capacitor
4. Transistor

Correct Option: 1. Transformer

Explanation: A transformer is commonly used to step-up or step-down AC voltage levels. It consists of two or more coils of wire, known as windings, that are magnetically coupled. Transformers are essential in power distribution systems.

## Which theorem states that the maximum power is transferred from a source to a load when the load impedance matches the complex conjugate of the source impedance

Which theorem states that the maximum power is transferred from a source to a load when the load impedance matches the complex conjugate of the source impedance?

1. Superposition theorem
2. Norton’s theorem
3. Thevenin’s theorem
4. Maximum Power Transfer theorem

Correct Option: 4. Maximum Power Transfer theorem

Explanation: The Maximum Power Transfer theorem states that the maximum power is transferred from a source to a load when the load impedance matches the complex conjugate of the source impedance. This theorem helps optimize power transfer efficiency.

## Which of the following is true about an open circuit

Which of the following is true about an open circuit?

1. It allows current flow.
2. It has infinite resistance.
3. It has zero voltage.
4. It is a short circuit.

Correct Option: 2. It has infinite resistance.

Explanation: An open circuit is a circuit that has a break or interruption, preventing current flow. It has infinite resistance because there is no complete path for the current to follow.

## Which law relates the voltage, current, and resistance in an electrical circuit

Which law relates the voltage, current, and resistance in an electrical circuit?

1. Ohm’s Law
3. Lenz’s Law
4. Ampere’s Law

Correct Option: 1. Ohm’s Law

Explanation: Ohm’s Law states that the current flowing through a conductor is directly proportional to the voltage applied across it and inversely proportional to its resistance. It is represented by the equation I = V/R.

## Which component is commonly used to protect other components in a circuit by limiting the amount of current that can flow through them

Which component is commonly used to protect other components in a circuit by limiting the amount of current that can flow through them?

1. Resistor
2. Capacitor
3. Inductor
4. Fuse

Correct Option: 4. Fuse

Explanation: A fuse is a safety device used to protect other components in a circuit by limiting the amount of current that can flow through them. When the current exceeds a certain threshold, the fuse melts, breaking the circuit and preventing damage to the components.

## What is the purpose of a ground in an electrical circuit

What is the purpose of a ground in an electrical circuit?

1. To provide a reference point for voltage measurements.
2. To regulate the flow of current.
3. To increase the resistance in the circuit.
4. To store electrical energy.

Correct Option: 1. To provide a reference point for voltage measurements.

Explanation: The ground in an electrical circuit serves as a reference point for voltage measurements. It is typically connected to the earth or a common reference point and allows for consistent and accurate voltage measurements.

## Which of the following is a passive component

Which of the following is a passive component?

1. Transistor
2. Diode
3. Resistor
4. Op-amp

Correct Option: 3. Resistor

Explanation: A resistor is a passive component that restricts the flow of current in a circuit. It is widely used to control current levels, divide voltage, and limit power dissipation.

## Which law states that the algebraic sum of currents entering a node is equal to the algebraic sum of currents leaving the node

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

1. Kirchhoff’s Current Law
2. Kirchhoff’s Voltage Law
3. Ohm’s Law