Capacitor and Capacitance: Working, Important Formulas and Real-Life Applications

Capacitor and capacitance are important concepts in electronics. A capacitor is an electronic device that stores electrical energy, while capacitance is the measure of how much electric charge a capacitor can store at a given voltage. Capacitors are widely used in devices such as mobile phones, televisions, computers, cameras, and power supply circuits. This article explains capacitors and capacitance, their working, formula, factors affecting capacitance, and real-life applications in simple and student-friendly language.

Table of Contents

• What is a Capacitor and Capacitance
• How Does a Capacitor Work
• How Is Capacitance Measured
• How to Calculate Energy Stored in a Capacitor
• Capacitance of a Parallel Plate Capacitor
• Real-Life Applications of Capacitors

What is a Capacitor and Capacitance

A capacitor is a two-terminal electrical device that stores electrical energy in the form of electric charge. It consists of two conducting plates separated by a small gap. This gap is filled with an insulating material called a dielectric, or sometimes it may simply contain air or a vacuum.

The ability of a capacitor to store electric charge is called capacitance. In simple words,

“Capacitance tells us how much electric charge a capacitor can store for a given voltage.”

Imagine two empty water tanks connected to a pipe. The larger the tanks, the more water they can hold. In a similar way, a capacitor stores electric charge between its two plates.

Interestingly! Capacitors come in different shapes, sizes, and materials depending on where they are used. One of the simplest and most common designs is the parallel plate capacitor, which consists of two flat metal plates placed close to each other.

How Does a Capacitor Work

Consider a parallel plate capacitor connected to a battery. One plate is connected to the positive terminal, while the other plate is connected to the negative terminal. Although the battery supplies electric charge, the charges cannot move directly from one plate to the other because the plates are separated by the insulating dielectric material.

As the battery remains connected, positive charges collect on one plate, while an equal amount of negative charges gather on the other plate. This creates an electric field between the two plates, and the capacitor starts storing electrical energy.

Charging of a Capacitor

During the charging process,

• The positive plate collects positive charges.
• The negative plate collects negative charges.
• An electric field develops between the plates.
• The capacitor continues storing charge until it reaches its maximum capacity for the applied voltage.

This process is known as charging a capacitor.

Now, you may ask what happens when the battery is removed.

Even after disconnecting the battery, the capacitor keeps the stored charges on its plates for a short period. Because of this stored energy, it can act as a temporary source of electrical energy.

Discharging of a Capacitor

When the two plates are connected through an electrical circuit or a load, the stored charges begin to move through the circuit. As the charges leave the plates, the stored energy is gradually released until the capacitor becomes fully discharged.

This process is called the discharging of a capacitor.

How Is Capacitance Measured

Capacitance tells us how effectively a capacitor can store electric charge when a voltage is applied across its plates.

The relationship between charge and voltage is shown by the formula:

Capacitance (C) = Charge (Q) ÷ Voltage (V)

Where C is the capacitance measured in farads (F), Q is the electric charge stored on the capacitor, and V is the potential difference across its plates.

So, in simple words, if a capacitor can hold a large amount of charge at the same voltage, its capacitance is higher.

But here's something interesting!

Many students think capacitance changes only because of charge or voltage. In reality, the construction of the capacitor plays a much bigger role.

The value of capacitance mainly depends on, 

• The size of the conducting plates: Larger plates can store more charge.
• The distance between the plates: Plates placed closer together provide higher capacitance.
• The dielectric material: Different insulating materials affect how much charge the capacitor can store.

Now you may ask, can the value of capacitance always remain the same?

Not necessarily. Some capacitors are made with a fixed capacitance, while others have variable capacitance, allowing their value to be adjusted for different electronic circuits.

How to Calculate Energy Stored in a Capacitor

Imagine charging a capacitor and then disconnecting it from the power supply. Even after the battery is removed, the capacitor can still provide electrical energy for a short time. This happens because it stores energy in the electric field formed between its two conducting plates.

The amount of energy stored depends on the capacitor's capacitance and the voltage applied across it. It can be calculated using the following formula:

E=12CV2

Where E is the energy stored (joules, J), C is the capacitance (farads, F), and V is the voltage across the capacitor (Volt, V).

Now you may ask, is a capacitor the same as a battery?

Not exactly. Although both can store energy, they do so in different ways. A battery stores energy through chemical reactions, while a capacitor stores energy by separating positive and negative charges between its plates. Because of this, a capacitor can charge and release energy much more quickly than a battery.

Capacitance of a Parallel Plate Capacitor

A parallel plate capacitor consists of two flat metal plates placed parallel to each other. These plates are separated by a small gap filled with air, vacuum, or an insulating material called a dielectric. 

When a voltage is applied across the plates, one plate becomes positively charged while the other becomes negatively charged. As a result, the capacitor begins storing electric charge.

Factors Affecting Capacitance

The capacitance of a parallel plate capacitor mainly depends on three things:

• Area of the plates (A): Larger plates can hold more electric charge, so the capacitance increases.
• Distance between the plates (d): When the plates are placed closer together, the capacitance becomes higher.
• Dielectric material (ε): Using a material with a higher dielectric constant increases the capacitance.

The capacitance of a parallel plate capacitor is calculated using the formula:

C=εAd

Where C is capacitance (Farad, F), ε is the permittivity of the dielectric material, A is the area of each conducting plate, and d is the distance between the two plates

Interestingly! This formula shows that capacitance is directly proportional to the area of the plates and inversely proportional to the distance between them. 

Real-Life Applications of Capacitors

Capacitors are widely used in electrical and electronic devices because they can store and release electrical energy whenever needed.

• Power Supply Circuits: Help maintain a steady voltage and protect electronic components.
• Mobile Phones and Computers: Support electronic circuits and improve device performance.
• Camera Flash: Stores energy and releases it instantly to produce a bright flash.
• Electric Motors: Help start and run appliances such as fans, refrigerators, and air conditioners.
• Communication Systems: Improve signal quality in radios, televisions, and other communication devices.
• Touchscreen Devices: Detect finger touches in smartphones and tablets.

Interestingly! From household appliances to modern electronic gadgets, capacitors play an important role in making devices work efficiently and reliably.

In this article, we learned that capacitors and capacitance are important concepts in electronics that help store and release electrical energy. We also studied what is a capacitor and capacitance, how a capacitor works, how capacitance is measured, the energy stored in a capacitor, and the capacitance of a parallel plate capacitor.