Capacitors are one of the most popular and commonly used electronic components in electrical devices and components. They are critical for various applications, from simple circuits to complex electrical systems. Capacitors store and release electrical charge when needed, making them a crucial part of many electronic devices. The essential function of a capacitor is to store electrical energy. A capacitor does so using an electric field. Its basic construction involves two conductive plates separated by a dielectric material usually made of ceramic, plastic, or paper. When a potential difference is provided to the capacitor, electrical charge accumulates on the plates, creating an electric field between them. The electric field stores electrical energy. Capacitors are available in many shapes and sizes, depending on their intended use and applications. They can be found in everything from small electronic devices to large power systems. Some capacitors are designed for high-frequency applications, while others are optimized for high voltage or current. One of the most common applications for capacitors is in power supplies. They are used to smooth out the voltage fluctuations in AC power, ensuring a stable and reliable power supply for electronic devices. Audio equipment also uses capacitors to filter out unwanted noise and interference. Electrical Engineering Online shares MCQ Questions on Capacitors with brief explanatory answers and solutions.

## Which of the below-mentioned is a property of a capacitor

Which of the below-mentioned is a property of a capacitor

- Resistance
- Inductance
- Capacitance
- Conductance

Correct Answer: 3. Capacitance

**Explanation:** Capacitance is the property of a capacitor that represents its ability to store electrical energy.

## Which unit is used to measure capacitance

Which unit is used to measure capacitance

- Volts
- Amperes
- Farads
- Ohms

Correct Answer: 3. Farads

**Explanation:** Farads (F) is the unit of capacitance. It is named after the physicist Michael Faraday.

## What is the symbol used to represent a capacitor in an electrical circuit?

What is the symbol used to represent a capacitor in an electrical circuit?

- R
- C
- L
- I

Correct Answer: 2. C

**Explanation:** The letter “C” commonly represents a capacitor in circuit diagrams.

## What happens to the capacitance of a given capacitor if the distance between its plates is increased

What happens to the capacitance of a given capacitor if the distance between its plates is increased?

- Increases
- Decreases
- Remains the same
- Becomes zero

Correct Answer: 2. Decreases

**Explanation:** The capacitance of a capacitor is inversely proportional to the distance between its plates. Increasing the distance decreases the capacitance.

## Which of the following factors affects the capacitance of a capacitor

Which of the following factors affects the capacitance of a capacitor

- Plate area
- Dielectric material
- Plate separation
- All of the above

Correct Answer: 4. All of the above

**Explanation:** The capacitance of a capacitor depends on the plate area, dielectric material, and plate separation.

## What is the purpose of a dielectric material in a capacitor

What is the purpose of a dielectric material in a capacitor

- It increases the capacitance
- It decreases the capacitance
- It controls the flow of current
- It provides mechanical support

Correct Answer: 1. It increases the capacitance

**Explanation:** A dielectric material inserted between the plates of a capacitor increases the capacitance by reducing the electric field strength.

## What happens to the capacitance of a capacitor if a dielectric material with a higher permittivity is used

What happens to the capacitance of a capacitor if a dielectric material with a higher permittivity is used?

- Increases
- Decreases
- Remains the same
- Becomes zero

Correct Answer: 1. Increases

**Explanation:** The capacitance of a capacitor increases when a dielectric material with a higher permittivity (relative permittivity or dielectric constant) is used.

## In a series combination of capacitors, the total capacitance is

In a series combination of capacitors, the total capacitance is:

- The sum of individual capacitances
- The reciprocal of the sum of individual capacitances
- The average of individual capacitances
- The maximum of individual capacitances

Correct Answer: 2. The reciprocal of the sum of individual capacitances

Explanation: In a series combination, the reciprocal of the total capacitance is equal to the sum of the reciprocals of the individual capacitances.

## In a parallel combination of capacitors, the total capacitance is

In a parallel combination of capacitors, the total capacitance is:

- The sum of individual capacitances
- The reciprocal of the sum of individual capacitances
- The average of individual capacitances
- The maximum of individual capacitances

Correct Answer: 1. The sum of individual capacitances

**Explanation:** In a parallel combination, the total capacitance equals the sum of the individual capacitances.

## Which of the below mentioned remark is true when a charged capacitor is connected in parallel with an uncharged capacitor

Which of the below mentioned remark is true when a charged capacitor is connected in parallel with an uncharged capacitor?

- The charge on the charged capacitor decreases
- The voltage across the charged capacitor decreases
- The total energy stored in the capacitors decreases
- The total capacitance of the capacitors increases

Correct Answer: 4. The total capacitance of the capacitors increases

**Explanation:** When capacitors are connected in parallel, the total capacitance increases as the individual capacitances add up. The charges and voltages across the capacitors remain unchanged.

## What is the time constant of an RC circuit

What is the time constant of an RC circuit?

- The time taken for the voltage across capacitor to reach 63.2% of its maximum value
- The time taken for the capacitor to charge fully
- The time taken for the voltage across the resistor to reach 63.2% of its maximum value
- The time is taken for the circuit to reach a steady state

Correct Answer: 1. The time taken for the voltage across capacitor to reach 63.2% of its maximum value

Explanation: The time constant (τ) of an RC circuit is defined as the time it takes for the voltage across the capacitor to reach approximately 63.2% (1 – 1/e) of its maximum value during charging or discharging.

## In an AC circuit, the capacitive reactance is given by

In an AC circuit, the capacitive reactance is given by:

- Xc = 1 / (2πfC)
- Xc = 2πfC
- Xc = R / C
- Xc = 1 / (2πRC)

Correct Answer: 1. Xc = 1 / (2πfC)

**Explanation:** The capacitive reactance (X3. in an AC circuit is inversely proportional to the frequency (f) and the capacitance (3. and is given by Xc = 1 / (2πfC).

## What happens to a capacitor’s capacitive reactance if the AC signal’s frequency increases

What happens to a capacitor’s capacitive reactance if the AC signal’s frequency increases?

- Increases
- Decreases
- Remains the same
- Becomes zero

Correct Answer: 2. Decreases

**Explanation:** A capacitor’s capacitive reactance decreases as the AC signal frequency increases. It is inversely proportional to the frequency.

## Which of the following circuits can act as a high-pass filter

Which of the following circuits can act as a high-pass filter

- RC circuit
- RL circuit
- LC circuit
- RLC circuit

Correct Answer: 1. RC circuit

**Explanation:** An RC circuit can act as a high-pass filter, allowing high-frequency signals to pass while attenuating low-frequency signals.

## What is the effect of adding a capacitor in parallel to a resistor in a DC circuit

What is the effect of adding a capacitor in parallel to a resistor in a DC circuit

- Increases the resistance of the circuit
- Decreases the resistance of the circuit
- Increases the time constant of the circuit
- Decreases the time constant of the circuit

Correct Answer: 4. Decreases the time constant

## When a capacitor is fully charged in a DC circuit, what happens to the current flowing through it

When a capacitor is fully charged in a DC circuit, what happens to the current flowing through it

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

Correct Answer: 1. The current becomes zero

**Explanation:** Once a capacitor is fully charged in a DC circuit, the flow of current stops as the capacitor acts as an open circuit for DC.

## What is the phase relationship between the voltage and current in a capacitive AC circuit

What is the phase relationship between the voltage and current in a capacitive AC circuit

- The voltage leads the current by 90 degrees
- The voltage lags the current by 90 degrees
- The voltage and current are in phase.
- The phase relationship depends on the frequency

Correct Answer: 2. The voltage lags the current by 90 degrees.

**Explanation:** In a purely capacitive AC circuit, the voltage across the capacitor lags the current by 90 degrees.

## What happens if a DC voltage source is connected directly across a capacitor

What happens if a DC voltage source is connected directly across a capacitor

- The capacitor charges to the total voltage
- The capacitor discharges, and no voltage is present
- The capacitor blocks the DC voltage
- The capacitor explodes due to excessive voltage

Correct Answer: 1. The capacitor charges to the full voltage.

Explanation: When a DC voltage source is connected directly across a capacitor, the capacitor charges up to the same voltage as the source.

## Which of the below mentioned materials is commonly used as a dielectric in capacitors

Which of the below mentioned materials is commonly used as a dielectric in capacitors?

- Copper
- Aluminum
- Paper
- Ceramic

Correct Answer: 4. Ceramic

Explanation: Ceramic is a common dielectric material used in capacitors due to its high dielectric constant and stability.