Inductors are a fundamental component of many electrical circuits. They are used for various applications, including energy storage, filtering, and signal processing. Inductors are passive electronic components that store energy in a magnetic field. Inductors are also sometimes known as coils, chokes, or reactors. Their properties depend on their physical construction and the materials used. The basic construction of an inductor involves a coil of wire wound around a core made of a magnetic material. The number of turns of wire in the coil, the diameter of the wire, and the core material all affect the inductor’s properties. The inductance of an inductor is a measure of its ability to store energy in a magnetic field, measured in henries. Inductors can be used in various applications, including power supplies, filters, and oscillators. They are handy in circuits that require energy storage, such as in DC-DC converters. In these circuits, the inductor smooths out the voltage, preventing spikes and drops that could cause damage to the circuit. Inductors are also employed in filter circuits, which block unwanted frequencies and allow only the desired frequencies to pass. They are commonly used in audio circuits, where they can be used to remove noise from a signal or to enhance specific frequencies. Another common application of inductors is in oscillators, where they are used to create a stable frequency. In these circuits, the inductor and capacitor work together to create a resonant circuit, which oscillates at a specific frequency. In this post Electrical Engineering Online shares Objective Electrical MCQ Questions on Earthing and Grounding.

## Which of the following statements about inductors is true

Which of the following statements about inductors is true

- They store energy in an electric field
- They oppose changes in current
- They have a constant resistance
- They have no effect on AC circuits

Correct Answer: 2. They oppose changes in current

**Explanation:** Inductors resist changes in current flow and store energy in a magnetic field, not an electric field.

## What is the unit of inductance

What is the unit of inductance?

- Ohm
- Ampere
- Henry
- Farad

Correct Answer: 3. Henry

Explanation: The unit of inductance is the Henry (H)

## The inductance of an inductor depends on which of the following factors

The inductance of an inductor depends on which of the following factors?

- Number of turns
- Cross-sectional area of the coil
- Permeability of the core material
- All of the above

Correct Answer: 4. All of the above

**Explanation:** The inductance of an inductor depends on the number of turns, the coil’s cross-sectional area, and the core material’s permeability.

## When the current through the inductor changes, what happens to the voltage across it

When the current through the inductor changes, what happens to the voltage across it?

- The voltage remains constant
- The voltage decreases
- The voltage increases
- The voltage oscillates

Correct Answer: 3. The voltage increases.

**Explanation:** When the current through the inductor changes, the inductor generates a voltage that opposes the change in current, resulting in an increase in voltage across the inductor.

## What happens to the inductance of an inductor when an iron core is inserted

What happens to the inductance of an inductor when an iron core is inserted?

- The inductance decreases
- The inductance remains the same
- The inductance increases
- The inductance becomes zero

Correct Answer: 3. The inductance increases.

**Explanation:** Inserting an iron core into an inductor increases its inductance by providing a higher permeability path for the magnetic field.

## In an AC circuit, the impedance of an inductor is proportional to which of the following

In an AC circuit, the impedance of an inductor is proportional to which of the following

- Frequency
- Voltage
- Current
- Inductance value

Correct Answer: 1. Frequency

**Explanation:** The impedance of an inductor in an AC circuit is proportional to the frequency of the alternating current.

## What happens to the reactance of an inductor as the frequency increases

What happens to the reactance of an inductor as the frequency increases

- The reactance increases
- The reactance decreases
- The reactance remains constant
- The reactance becomes zero

Correct Answer: 1. The reactance increases

**Explanation:** The reactance of an inductor is directly proportional to the frequency, so as the frequency increases, the reactance of the inductor also increases.

## When an inductor is connected in series with a resistor, the total impedance is given by

When an inductor is connected in series with a resistor, the total impedance is given by:

- Z = R + XL
- Z = R – XL
- Z = R / XL
- Z = XL / R

Correct Answer: 1. Z = R + XL

**Explanation:** When an inductor is connected in series with a resistor, the total impedance is the sum of the resistance (R) and the inductive reactance (XL).

## What happens to the current in an inductor when the applied voltage across it is suddenly removed

What happens to the current in an inductor when the applied voltage across it is suddenly removed?

- The current decreases gradually
- The current decreases rapidly
- The current remains constant
- The current increases rapidly

Correct Answer: 2. The current decreases rapidly.

**Explanation:** When the applied voltage across an inductor is suddenly removed, the inductor opposes the change and tries to maintain the current. As a result, the current in the inductor decreases rapidly.

## In an RL circuit, if the resistance is increased, what happens to the circuit’s time constant

In an RL circuit, if the resistance is increased, what happens to the circuit’s time constant?

- The time constant increases
- The time constant decreases
- The time constant remains the same
- The time constant becomes zero

Correct Answer: 3. The time constant remains the same

**Explanation:** The time constant of an RL circuit depends only on the inductance and resistance values and is given by τ = L/R. Changing the resistance value does not affect the inductance, so the time constant remains unchanged.

## Which of the following is a typical application of an inductor

Which of the following is a typical application of an inductor?

- Voltage regulation
- Signal amplification
- Data storage
- Logic operations

Correct Answer: 1. Voltage regulation

**Explanation:** Inductors are commonly used in voltage regulation circuits, such as DC-DC converters and power supplies, to stabilize and filter the output voltage.

## When two inductors are connected in series, their total inductance is

When two inductors are connected in series, their total inductance is:

- The sum of their individual inductances
- The average of their individual inductances
- The product of their individual inductances
- The reciprocal of their individual inductances

Correct Answer: 1. The sum of their individual inductances.

**Explanation:** When inductors are connected in series, their total inductance is simply the sum of their individual inductance values.

## What happens to the magnetic field strength inside an inductor when the current flowing through it increases

What happens to the magnetic field strength inside an inductor when the current flowing through it increases?

- The magnetic field strength increases
- The magnetic field strength decreases
- The magnetic field strength remains constant
- The magnetic field strength becomes zero

Correct Answer: 1. The magnetic field strength increases.

**Explanation:** The magnetic field strength inside an inductor is directly proportional to the current flowing through it. Therefore, the magnetic field strength inside the inductor increases when the current increases.

## What is the purpose of a flyback diode connected across an inductor in a circuit

What is the purpose of a flyback diode connected across an inductor in a circuit?

- To block the flow of current through the inductor
- To protect other components from voltage spikes
- To decrease the inductance value of the inductor
- To increase the resistance of the inductor

Correct Answer: 2. To protect other components from voltage spikes.

Explanation: A flyback diode (also known as a freewheeling diode) is connected across an inductor to provide a path for the current when the inductor is switched off. It protects other components from voltage spikes that occur when the magnetic field collapses.

Which of the following materials is commonly used as a core material in inductors

## Which of the following materials is commonly used as a core material in inductors?

- Copper
- Aluminum
- Iron
- Silver

Correct Answer: 3. Iron

Explanation: Iron is a common core material used in inductors due to its high permeability, which helps increase the inductance.

## What is the effect of adding a capacitor in parallel to an inductor in an AC circuit

What is the effect of adding a capacitor in parallel to an inductor in an AC circuit?

- It increases the impedance of the circuit
- It decreases the impedance of the circuit
- It has no effect on the impedance of the circuit
- It increases the resistance of the inductor

Correct Answer: 2. It decreases the impedance of the circuit.

Explanation: Adding a capacitor in parallel to an inductor forms an LC circuit, which can create resonance. This combination decreases the overall impedance of the circuit at the resonant frequency.

## When an inductor carries a steady DC current, which of the following statements is true

When an inductor carries a steady DC current, which of the following statements is true?

- The inductor produces a magnetic field that remains constant.
- The inductor does not produce a magnetic field.
- The inductor produces a magnetic field that gradually decays.
- The inductor produces a magnetic field that gradually increases.

Correct Answer: 1. The inductor produces a magnetic field that remains constant.

**Explanation: **When an inductor carries a steady DC current, the inductor produces a constant magnetic field that remains unchanged as long as the current is steady.

## Which of the following factors affects the self-inductance of a straight wire conductor

Which of the following factors affects the self-inductance of a straight wire conductor?

- Length of the wire
- Cross-sectional area of the wire
- Number of turns in the wire
- Material of the wire

Correct Answer: 1. Length of the wire

**Explanation: **The self-inductance of a straight wire conductor depends on the length of the wire. A longer wire will have higher self-inductance compared to a shorter wire, assuming other factors remain constant.

## What is the phase relationship between the current and voltage in an inductor in an AC circuit

What is the phase relationship between the current and voltage in an inductor in an AC circuit?

- The current leads the voltage by 90 degrees.
- The current lags the voltage by 90 degrees.
- The current lags the voltage by 90 degrees.
- None of above

**Explanation: **In an inductor in an AC circuit, the current lags the voltage by 90 degrees. This means that the current waveform reaches its maximum value after the voltage waveform reaches its maximum value.