Capacitors for Beginners: Types, Uses & How to Choose

Capacitors are widely used in circuits for various functions, such as power regulation, noise suppression, and signal handling. Gaining a basic understanding of their roles and properties is essential for anyone new to electronics.

A capacitor is an electronic component used to store energy. Also known as a condensator or condenser in older terminology, a capacitor stores electrical energy by accumulating opposite charges on two plates separated by a dielectric.

Introduction to Capacitors
What Are Capacitors Made Of?
Types of Capacitors
- Fixed Capacitors
- Variable Capacitors
Capacitor Shapes and Mounting Styles
Capacitor Symbol in Circuit Diagrams
Applications of Capacitors
Capacitor Values and Voltage Ratings
Capacitors in Hobby Electronics
History of Capacitors
New Developments in Capacitor Technology
Choosing the Right Capacitor
Capacitor FAQ for Beginners
Conclusion

Introduction to Capacitors

These components are fundamental in electronics. They are used for storing electrical energy, filtering signals, and handling different voltage levels. A capacitor is a passive electrical part with two terminals. It stores energy in the electric field created between its internal plates. They are available in many forms and made from various materials, each tailored to specific purposes.

What Are Capacitors Made Of?

Every capacitor contains two conductive plates. These are separated by an insulating layer known as the dielectric. The type of dielectric material used directly impacts the performance. Common examples include ceramic, tantalum, electrolytic, polyester, and mica.

Each material affects factors like voltage tolerance, capacitance value, and application suitability. When designing a circuit, it’s important to choose the correct type for the task at hand.

Types of Capacitors

Electronic circuits use a variety of capacitor types. Each one serves a particular role depending on its design and capabilities.

Fixed Capacitors

These have a constant capacitance. They are frequently chosen for stable and repeatable performance.

Ceramic – These are widely available and come in styles like X7R, NPO, and disc.
Electrolytic – This includes aluminum and tantalum types, ideal for power filtering.
Film – Examples include polyester, Mylar, and polypropylene.
Mica – Favored in high-frequency setups.
Paper – Found in older designs but still used occasionally.
Supercapacitors – Also called ultracapacitors, they store large energy amounts for specific needs.

Variable Capacitors

These allow the user to adjust the capacitance manually or electronically. They’re often used in frequency control and tuning applications.

Trimmers – Small and adjustable.
Tuning – Used mainly in radios.
Vacuum variable – Designed for high-voltage conditions.

Capacitor Shapes and Mounting Styles

These components come in several shapes and configurations, designed to fit different board layouts.

Through-hole types – These include radial and axial leads.
Surface-mount types – Common examples are ceramic, tantalum, and electrolytic SMDs.

Surface mount ceramic capacitors on a circuit board — Surface Mount Ceramic Capacitors on a Circuit Board

Surface mount electrolytic capacitors on a circuit board — Surface Mount Electrolytic Capacitors on a Circuit Board

Capacitor Symbol in Circuit Diagrams

When reading electronic schematics, it’s important to recognize the capacitor symbol so you can correctly identify where capacitors are used in a circuit. Capacitor symbols represent the type and function of the capacitor being used, and different symbols exist for different types, such as polarized, non-polarized, variable, and specialty capacitors. Additionally, there are slight differences between how polarized capacitor symbols are drawn in the United States (ANSI standards) and in Europe (IEC standards).

Understanding these symbols is essential for interpreting circuit diagrams, troubleshooting, or designing electronic systems.

Standard Capacitor Symbol (Non-Polarized)

Both the American and European standards use the same symbol for non-polarized capacitors. It consists of two straight, parallel lines, representing the two plates separated by a dielectric, as shown below.

Polarized Capacitor Symbol (Electrolytic and Tantalum)

Polarized Capacitor Symbol (ANSI – U.S. Standard)

The ANSI symbol for polarized capacitors shows one straight line and one curved line. The straight line indicates the positive terminal, while the curved line indicates the negative terminal. This symbol is common in many educational and schematic contexts.

Polarized Capacitor Symbol (IEC – European Standard)

The IEC symbol for polarized capacitors uses two straight lines, but one is drawn as a solid (filled) rectangle, representing the negative terminal. The other is a thin, unfilled box or line, indicating the positive side. This clear distinction helps prevent polarity errors in circuit design.

Variable Capacitor Symbol

A variable capacitor is shown by adding an arrow through or across the standard capacitor symbol, indicating that the capacitance can be adjusted. These capacitors are often used in tuning circuits such as radios.

In both U.S. and EU styles, the variable indicator (arrow) is used, as the image below shows.

Trimmer Capacitor Symbol

A trimmer capacitor is a type of small, adjustable capacitor used for calibration. Its symbol is similar to that of a variable capacitor but typically includes a line at the end of the slanted line instead of an arrow head to indicate a semi-fixed setting.

Applications of Capacitors

Capacitors have a broad range of practical uses. Here’s a look at how they’re used across several categories.

Power Supply

They help maintain voltage stability and remove unwanted noise. This improves power supply efficiency and reliability.

Filtering components smooth voltage irregularities.
Power factor correction improves AC efficiency.
DC blocking units allow alternating current to pass while blocking direct current.

Audio Circuits

Sound systems rely heavily on these components. They manage frequencies and help shape the audio signal.

Used in amplifiers to block noise.
Subwoofers and crossovers benefit from large-value models.
Car audio often includes 1-farad or bipolar versions.

Motors

Motors need special types of capacitors to start and run smoothly.

Start types provide high torque at startup.
Run types stay active during operation.
Fan and compressor capacitors are designed for specific electric motor needs.

High Voltage and Specialty Uses

Industrial systems require specially rated capacitors for demanding tasks.

High-voltage models power machinery and microwave systems.
Snubber and surge variants protect from spikes and transients.
Shunt models help control reactive power in AC networks.

Capacitor Values and Voltage Ratings

Capacitance is measured in farads, ranging from tiny picofarad units to large farad sizes.

Examples:

Small: 100pF, 10nF, 100nF, 1µF
Medium: 10µF, 100µF
Large: 1000µF, 1F, 10F

Voltage ratings vary from low, for example 12V, to thousands of volts in industrial versions.

Capacitors in Hobby Electronics

Capacitors are a staple in hobby electronics projects, and one of the most common types you’ll encounter is the radial through-hole capacitor. These capacitors have two leads coming out of the same end, making them easy to insert into breadboards and stripboards. For beginners and makers, capacitor kits are a great way to build up a selection of commonly used values for prototyping and learning.

A radial through-hole electrolytic capacitor — A Radial Through-hole Electrolytic Capacitor

Capacitor Kits for Electronics Projects

A typical capacitor assortment kit contains a variety of values that cover a broad range of functions in basic circuits. For example, a 30-piece kit might include:

5 x 100nF (0.1µF) – often used for decoupling and noise filtering.
5 x 22pF – commonly used in crystal oscillator circuits.
5 x 10µF, 100µF, 220µF, and 1000µF – used for timing, power supply smoothing, and energy storage.

These capacitors often have voltage ratings of 35V to 50V, making them safe for most low-voltage hobby projects.

The following image shows the contents of a basic capacitor kit, as described in the above list.

Reading Capacitor Values

Radial capacitors are usually marked with their capacitance and voltage rating directly on the body. For electrolytic capacitors, the value is typically printed as “10µF 50V”, for example.

Ceramic disc capacitors may use a three-digit code like “104” (which means 10 followed by 4 zeros in picofarads), which is 100,000 pF (one hundred thousand picofarads). This can also be written as 100nF (one hundred nanofarads) or 0.1 µF (zero point one microfarads). Or in other words 100,000pF is the same as 100nF which is the same as 0.1µF. These are all ways of expressing the same value in different units. Understanding these markings is essential when selecting components for your circuits.

Using Capacitors on a Breadboard

Because of their lead spacing and form factor, radial capacitors are ideal for use on a breadboard. You can easily place them across power rails to filter supply voltage, between signal lines for coupling, or in timing circuits using 555 timers. Their compatibility with standard 2.54mm (0.1 inch) pitch makes them beginner-friendly and perfect for fast prototyping.

Simple Circuits Using Hobby Capacitors

Here are some common circuits where these kit capacitors are useful:

555 Timer Circuits: Use a 10µF or 100µF capacitor with resistors to set timing intervals for blinking LEDs or tone generation.
Decoupling Power Rails: Place 100nF capacitors near ICs to reduce voltage spikes and noise.
Oscillator Circuits: 22pF capacitors are used with crystals in microcontroller clock circuits.
Audio Coupling: Use 10µF to 100µF capacitors to pass audio signals between amplifier stages.
Power Supply Smoothing: 220µF and 1000µF electrolytic capacitors are excellent for smoothing out rectified DC voltage from wall adapters or batteries.

Whether you’re experimenting with your first Arduino project or building a custom audio circuit, having a kit of capacitors on hand makes it much easier to test ideas and build working prototypes.

History of Capacitors

Capacitor technology has evolved significantly. From early Leyden jars to today’s polymer types, the journey includes countless innovations in dielectric materials and design techniques.

Originally invented in the 18th century, they’ve become key players in modern electronics—moving from paper-based versions to reliable, high-performance components.

New Developments in Capacitor Technology

Recent advancements focus on better efficiency and longevity.

Solid-state types improve reliability.
Electric double-layer variants store more energy.
Polymer models deliver superior performance in power circuits.
Self-healing designs last longer under stress.

Choosing the Right Capacitor

Selecting the right component depends on several criteria:

Purpose – such as audio, motors, or power supply.
Value – Choose based on µF, nF, or pF.
Voltage – Match or exceed circuit requirements.
Form factor – Use SMD or through-hole as needed.

Capacitor FAQ for Beginners

1. What is a capacitor?

It’s a two-terminal electronic part that stores and releases energy. Commonly used for filtering and energy management.

2. What are the main types of capacitors?

Popular varieties include ceramic, film, electrolytic, tantalum, and supercapacitors.

3. How do I read capacitor values?

Capacitor values are measured in farads (F). Common subunits are:

Microfarads (µF) – 1µF = 1 millionth of a farad.
Nanofarads (nF) – 1nF = 1 billionth of a farad.
Picofarads (pF) – 1pF = 1 trillionth of a farad.
Many capacitors have a three-digit code (e.g., 104 means 100,000 pF or 0.1 µF).

4. What’s the difference between polarized and non-polarized capacitors?

Polarized types must be installed in a specific direction. Non-polarized ones work either way.

5. What is a start capacitor vs. a run capacitor?

Start capacitors provide a high-energy boost to start electric motors. They are temporary and switch off once the motor starts.
Run capacitors help maintain efficient motor operation and stay active while the motor runs.

6. What is the difference between capacitors in series and capacitors in parallel?

In series: The total capacitance decreases, but the voltage rating increases.
In parallel: The total capacitance increases, but the voltage rating stays the same.

7. How do I choose the right capacitor for my project?

Consider these factors:

Capacitance value (µF, nF, pF) – Based on circuit requirements.
Voltage rating (V) – Must be higher than the circuit voltage.
Type (ceramic, electrolytic, film, etc.) – Depends on application.
Size and mounting (through-hole or SMD) – Based on space and assembly method.

8. What is a power factor correction capacitor?

These capacitors improve efficiency in AC power systems by reducing reactive power losses. They are used in industrial and large electrical setups.

9. Why do some capacitors explode or fail?

Common reasons include:

Overvoltage – Exceeding the rated voltage.
Reverse polarity – Connecting a polarized capacitor backward.
Excessive ripple current – Causing overheating.
Old age or poor quality – Electrolytic capacitors dry out over time.

For a detailed, step-by-step guide on testing capacitors with a multimeter, see our full tutorial on how to perform a multimeter capacitor test.

10. Can I replace a capacitor with a different value?

You should match or slightly exceed the voltage rating. Capacitance can sometimes be adjusted slightly, but large differences may affect circuit performance.

Conclusion

Capacitors are essential in electronics, serving functions from energy storage to noise filtering. Whether you need a power capacitor, bypass capacitor, dc capacitor, or electric motor capacitor, understanding their types, values, and applications will help you make the right choice for your projects.