What Is A Capacitor & Why Is It Important?

Capacitors are key electronic parts often overlooked but vital. They store and release electrical energy, crucial in many circuits. Knowing about capacitors is a must for electronics enthusiasts and tech learners. They do various jobs like smoothing power, filtering signals, and storing energy. Let’s uncover what makes capacitors important in today’s tech world.

Table of Contents

What is Capacitor?

Capacitor is also known as condenser. This is one of the passive components like resistor. Capacitor is generally used to store the charge. In capacitor the charge is stored in the form of “electrical field”. Capacitors play a major role in many electrical and electronic circuits.

Generally, a capacitor has two parallel metal plates which are not connected to each other. The two plates in the capacitor are separated by non conducting medium (insulating medium) this medium is commonly known as Dielectric.

There are different types and different shapes of capacitors available , from very small capacitors which are used in resonance circuits to large capacitors for stabilising HVDC lines. But all capacitors are doing the same work that is storing the electrical charge.

The shape of a capacitor is rectangular, square, circular, cylindrical or spherical shape. Unlike a resistor, an ideal capacitor does not dissipate energy. As the different types of capacitors are available different symbols were available to represent them which are shown below.

Why capacitors are important?

Capacitors have many properties like

They can store the energy and it can dissipate this energy to the circuit when ever required.
They can block DC and allow AC to flow through it, and this can couple one part of the circuit with the other.
Circuits with capacitors depend on the frequency, so can be used to amplify certain frequencies.
As the capacitors when applied with AC input , the current leads the voltage and thus in power applications it increases the pay load power and makes it more economical.
It allows high frequencies and so it can be used as a filters either to filter low frequencies or to collect high frequencies.
As the reactance and frequency of the capacitor are inversely related, this can be used to increase or decrease the circuit impedance at certain frequency and can be used as filter.

Likewise, capacitors exhibit many properties , when used in AC or DC circuits and hence they play important role in electrical and electronic circuits.

Construction of a Capacitor

As said before , there are different types of capacitors. These different types will have different type of construction. A Parallel plate capacitor is the simplest capacitor. Let us understand the construction of this capacitor.

It consists of two metal plate separated by a distance. The space between these two plates is filled with a dielectric material. The two leads of the capacitor are taken from these two plates.

The capacitance of the capacitor depends on the distance between the plates and area of the plates. Capacitance value can be changed by varying any of these parameters.

A variable capacitor can be constructed by making one of these plates fixed and other moving.

Dielectric Of a Capacitor

Dielectric acts as an insulating material between the plates . Dielectric can be any non conducting material such as ceramic, waxed paper, mica, plastic or some form of a liquid gel.

Dielectric also plays an important in deciding the value of capacitance. As the dielectric is introduced between the plates of the capacitor ,its value increases.

Different dielectric materials will have different dielectric constants ,however this value is >1.

Below table gives value of dielectric constant for each dielectric material

Dielectric can be of two types

Polar dielectrics: These dielectrics will have permanent dielectric movement
Non Polar dielectrics: These will have temporary dielectric moment. By placing them in a electric field they can be induced with dipole moments.

Complex Permittivity

The product of the relative permittivity (εr) of the dielectric material and permittivity of free space (εo) is known as “Complex permittivity” or “Actual permittivity” of the dielectric material. The expression for the complex permittivity is given as follows,

ε = ε0 * εr

The value of complex permittivity will always be equal to the relative permittivity, because the permittivity of free space is equal to ‘one’. The value of dielectric constant or complex permittivity varies from one dielectric material to another.

Some standard values of complex permittivity (ε) for common dielectric materials are Air = 1.0005, Pure Vacuum = 1.0000, Mica = 5 to 7, Paper = 2.5 to 3.5, Wood = 3 to 8, Glass = 3 to 10 and Metal Oxide Powders = 6 to 20 and etc.

capacitors can be classified according to the properties and characteristics of their insulating or dielectric material, they are given below as

High Stability & Low Loss Capacitors — Mica, Low-K Ceramic, and Polystyrene capacitors are examples for this type.
Medium Stability & Medium Loss Capacitors – Paper, Plastic Film, and High-K Ceramic capacitors are examples for this type.
Polarized Capacitors – Example for this type of capacitors are Electrolytic, Tantalum’s.

Working

As said before capacitor consists of two conductor separated by a dielectric , when there is any potential difference between the two conductors electric potential is developed.This causes the capacitor to charge and discharge.

Let us understand this in a practical way. When the capacitor is connected to a battery(a DC source) , current starts flowing through the circuit .

Thus negative charge is accumulated on one plate and positive charge is accumulated on the other plate. This process continuous until the capacitor voltage reaches supply voltage.

When the charging voltage is equal to the supply voltage capacitor stops charging further even though the battery is connected. When the battery is removed two plates will be accumulated with positive and negative charges. Thus the charge is stored in the capacitor.

But when the supply voltage is from an AC source it charges and discharges continuously .The rate of charging and discharging depends on the frequency of the source.

Example

Working can be understood using simple example here. Below circuit shows two switches A and B. When switch 1 is closed , current starts flowing from from the battery to the capacitor. When the capacitor voltage reaches the supply voltage ,it stops charging further.

Now connect the switch to position B. Now you can observe the LED starts glowing and this slowly fades out as the capacitor is discharging.

Capacitance of the capacitor is given by

C=KεA/d

C= εA/4πd

C = εo * εr (A/d)

Where,

C – Capacitance of the capacitor

A – Area between the plates

D – Distance between the two Plates

εo – Permittivity of free space

εr – Relative permittivity.

K- Dielectric Constant

Capacitance of a Capacitor

Capacitance is the property of the capacitor that defines the maximum amount of electrical charge stored in it.it exists in nature everywhere.

Capacitance may vary depending on the shape of the capacitor. Capacitance can be calculated by using the geometry of the conductors and dielectric material properties. Let us see the capacitance of a parallel plate capacitor.

Capacitance is defined as the ratio of charge (Q) on the either plates to the potential difference(V) between them ,

C =Q/V,

Thus current can be obtained as

I(t)=C[d(v)/d(t)]

This can can be expressed Farads (F) which is named after English physicist Michael Faraday.

From the above definition we can observe that capacitance is directly proportional to the charge (Q) and is inversely proportional to the voltage (V).

Capacitance of the capacitor can be increased by increasing the number of plates, which helps to maintain the same size of the capacitor. Here, area of the plates is increased.

Standard units of capacitance

Generally Farads is a high value so, capacitance is expressed as sub units of capacitor real time such as as micro farads(uF) , nano farads(nF) and pico farads(PF).

Most of the electrical and electronic applications are covered by the following standard unit (SI) prefixes for easy calculations,

1 mF (milli farad) = 10−3 F = 1000 μF = 1000000 nF
1 μF (microfarad) =10−6 F = 1000 nF = 1000000 pF
1 nF (nano farad) = 10−9 F = 1000 pF
1 pF (picofarad) = 10−12 F

To convert µF to nF or pF or to a wide range of other units and vice versa, we need to use the Electric Capacitance Unit Converter.

Voltage Rating of a Capacitor

This is not voltage until which the capacitor charges but the maximum voltage until which the capacitor can operate safely. This voltage is called as working voltage (WV) or DC working voltage (DC-WV).Below figure shows the voltage rating of the capacitor.

If the capacitor is applied with voltage greater than this voltage, it may be damaged by producing an arc between the plates due to dielectric break down.

While designing the circuits with capacitors, care should be taken such that the voltage rating of the capacitor is greater than the voltage used in the circuit. For example if the circuit operating voltage is 12V then it is necessary to choose a capacitor with voltage rating of 12V or above.

This working voltage of a capacitor depends on the factors like dielectric material used between the capacitor plates, dielectric thickness and also on the type of circuit which is used.

What is a Capacitor?

A capacitor is a passive electronic component that stores electrical energy in an electric field. It consists of two conductive plates separated by an insulating material known as a dielectric. When a voltage is applied across the plates, the capacitor stores energy until it’s discharged. Capacitors are widely used in circuits to smooth power, filter signals, and store energy for various applications.

Why is a Capacitor Important in Electronic Circuits?

Capacitors play a crucial role in electronic circuits by storing energy and releasing it when necessary. They help smooth power supplies, filter unwanted signals, and allow AC signals to pass while blocking DC currents. Capacitors are vital for frequency-dependent operations and help stabilize power in devices ranging from small electronics to high-voltage circuits.

What Are the Types of Capacitors?

There are several types of capacitors, including:

Ceramic Capacitors: Used in high-frequency applications.
Electrolytic Capacitors: Often used in power supplies due to their high capacitance values.
Tantalum Capacitors: Known for their stability and reliability.
Mica Capacitors: Offer low loss and high precision, used in RF circuits.

What is Capacitance?

Capacitance is the measure of a capacitor’s ability to store electrical charge. It is defined as the ratio of the charge stored to the voltage applied. The unit of capacitance is the farad (F). The greater the area of the plates and the smaller the distance between them, the higher the capacitance.

What is a Dielectric in a Capacitor?

The dielectric in a capacitor is an insulating material placed between the two conductive plates. It increases the capacitor’s capacitance by reducing the potential for electrical breakdown between the plates. Common dielectric materials include ceramic, paper, plastic, and mica.

How Does a Capacitor Work?

A capacitor stores energy when a voltage is applied across its plates. When the voltage reaches the same level as the supply voltage, the capacitor stops charging. In AC circuits, the capacitor charges and discharges continuously, with the rate determined by the frequency of the source.

What is the Voltage Rating of a Capacitor?

The voltage rating of a capacitor is the maximum voltage it can safely handle without damage. This rating is critical for ensuring that the capacitor operates within its safe limits to avoid dielectric breakdown and potential failure.

What Are the Different Capacitor Symbols?

Capacitors are represented by different symbols depending on their type. A basic capacitor is shown as two parallel lines, while an electrolytic capacitor has one curved line and one straight line to indicate its polarity.

What Are the Standard Units of Capacitance?

Capacitance is typically measured in farads (F). Since farads are a large unit, smaller units like microfarads (μF), nanofarads (nF), and picofarads (pF) are more commonly used in everyday electronic circuits.

How is Capacitance Calculated?

Capacitance can be calculated using the formula: $C = \frac{\epsilon_r \cdot A}{d}$ Where:

$C$ is capacitance
$\epsilon_r$ is the relative permittivity of the dielectric material
$A$ is the area of the plates
$d$ is the distance between the plates

What is the Role of a Capacitor in Power Supplies?

In power supplies, capacitors are used to smooth out fluctuations in voltage. They store charge when the voltage rises above the desired level and release it when the voltage drops, ensuring a steady supply of power.

What Are Polarized Capacitors?

Polarized capacitors, such as electrolytic capacitors, are designed to only work in one direction. They have polarity and must be connected correctly in the circuit. Reversing their polarity can cause damage or failure.

What is the Difference Between AC and DC Capacitors?

DC capacitors are used in direct current circuits, while AC capacitors are used in alternating current circuits. AC capacitors need to handle continuous charging and discharging due to the changing direction of the current.

What Happens if a Capacitor is Overvolted?

If a capacitor is subjected to a voltage higher than its rated voltage, the dielectric material can break down, causing the capacitor to fail. This can result in a short circuit, leaking current, or even physical damage.

How Does a Capacitor Affect Circuit Impedance?

Capacitors affect impedance in AC circuits. Since the reactance of a capacitor decreases with increasing frequency, capacitors can be used to filter signals, block low frequencies, and allow high frequencies to pass.

What Are the Applications of Capacitors in Everyday Electronics?

Capacitors are used in various devices, including:

Power supplies (to smooth voltage)
Radios (to filter frequencies)
Motor starters (to provide initial torque)
Flash cameras (to store energy for the flash)
Computers (for energy storage and filtering)

How Do Different Dielectric Materials Affect Capacitors?

The dielectric material in a capacitor affects its capacitance, stability, and voltage rating. For example, ceramic dielectrics are commonly used for low-cost, low-capacitance capacitors, while mica and tantalum capacitors are chosen for high precision and stability.

What Is a Variable Capacitor?

A variable capacitor is one whose capacitance can be adjusted. This is typically achieved by moving one of the plates to change the distance between the plates, allowing for tuning in circuits like radios.

What Is an Electrolytic Capacitor?

An electrolytic capacitor is a type of polarized capacitor with high capacitance values. It is commonly used in power supply circuits and energy storage applications due to its ability to store large amounts of energy in a small volume.

Can a Capacitor Fail?

Yes, capacitors can fail due to overvoltage, overcurrent, or physical damage. When a capacitor fails, it can short-circuit, leak, or explode, depending on the type and the nature of the failure.

How Do Capacitors Improve Signal Quality?

Capacitors can filter unwanted noise and smooth out voltage variations in signals. By blocking DC and allowing AC to pass, they help maintain the integrity of the signal in applications like audio equipment and communication devices.

Why Do Capacitors Have Different Shapes and Sizes?

The shape and size of a capacitor depend on its intended application. Larger capacitors are used for power storage, while smaller ones are used in high-frequency applications. Different shapes like cylindrical, rectangular, and square are used to optimize space and performance.

What Is the Importance of Capacitance in High-Frequency Circuits?

In high-frequency circuits, capacitors play an essential role in filtering and coupling signals. Their ability to store and release charge quickly makes them ideal for applications in radio frequency (RF) circuits, amplifiers, and oscillators.

Can Capacitors Be Used for Energy Storage?

Yes, capacitors are often used in applications where quick bursts of energy are required. They can store energy in their electric field and release it rapidly, making them useful in devices like camera flashes and power backup systems.

What Are Supercapacitors?

Supercapacitors, or ultracapacitors, are capacitors with extremely high capacitance values. They can store significantly more energy than traditional capacitors and are used in applications like electric vehicles and energy storage systems.

How Do Capacitors Help in Noise Reduction?

Capacitors help reduce electrical noise in circuits by filtering out high-frequency interference. This is essential in maintaining the performance of sensitive equipment like audio systems, radios, and computers.

Can Capacitors Be Recycled?

Yes, many capacitors can be recycled. However, it is important to follow proper recycling protocols because some capacitors, particularly electrolytic capacitors, can contain hazardous materials like heavy metals.