Capacitor

Capacitors (7189597135)

Types of capacitor

Leidse flessen Museum Boerhave december 2003 2

Radio Times - 1923-12-28 - page 39 - Dubilier

Capacitor schematic with dielectric

Capacitor is an electrical component used to store and release electricity in a circuit. It consists of two conductors (usually called plates) separated by an insulator (or dielectric). Capacitors are widely used in electronic circuits for various purposes, including filtering, buffering, and energy storage.

Overview

A capacitor works by accumulating electric charge on its plates when it is connected to a power source. The amount of electricity a capacitor can store is measured in Farads, a unit named after the English physicist Michael Faraday. The storage capacity of a capacitor, known as its capacitance, depends on the surface area of the plates, the distance between them, and the type of insulator used.

Types of Capacitors

There are several types of capacitors, each designed for specific applications and characteristics. These include:

• Electrolytic Capacitor: Known for their high capacitance values, these capacitors use an electrolyte as the dielectric. They are polarized, meaning they must be connected with the correct polarity in a circuit.
• Ceramic Capacitor: Made with ceramic material as the dielectric. They are non-polarized and are used in high-frequency applications like RF circuits.
• Film Capacitor: These capacitors use a thin plastic film as the dielectric. They are known for their stability and reliability over a wide range of temperatures and frequencies.
• Tantalum Capacitor: Tantalum capacitors offer high capacitance in a small package. They are polarized and used in spaces where size is a critical factor.
• Variable Capacitor: These capacitors allow the capacitance to be adjusted manually or electronically. They are commonly used in tuning circuits, such as radio receivers.

Applications

Capacitors have a wide range of applications in electronic circuits. Some of their primary uses include:

• Energy Storage: Capacitors can store and release energy quickly, making them ideal for use in power supply circuits.
• Filtering: In power supplies and audio circuits, capacitors are used to filter out unwanted frequencies.
• Signal Processing: Capacitors, in combination with resistors and inductors, are used to shape electrical signals in various ways.
• Timing and Oscillation: Capacitors are essential components in timing circuits and oscillators, determining the frequency of operation.

Principles of Operation

When a voltage is applied across the plates of a capacitor, an electric field is created in the dielectric, leading to the accumulation of positive charge on one plate and negative charge on the other. The ability of a capacitor to store charge is directly proportional to the plate area and inversely proportional to the plate separation. The dielectric material also affects the capacitance; materials with a higher dielectric constant can store more charge.

Safety Considerations

Capacitors, especially those with high capacitance values, can store a significant amount of energy. This can pose a risk of electric shock or damage to electronic components if not handled properly. It is important to discharge capacitors before working on any circuit they are part of.

See Also

• Resistor
• Inductor
• Electronic Circuit
• Electric Charge