Capacitor

A capacitor is a passive electronic component characterized by its ability to store electrical energy in an electric field. It consists of two conductive plates separated by an insulating material known as the dielectric. By applying a voltage across the plates, an electric field is created, causing an accumulation of positive charge on one plate and negative charge on the other, thus storing energy. This ability to store and release electrical energy rapidly makes capacitors fundamental in various electronic circuits. Capacitors are commonly used for power factor correction, smoothing output in power supplies, tuning resonant circuits, and performing timing functions in oscillators and filters. Their behavior is defined by their capacitance, measured in farads, which determines the amount of charge they can store at a given voltage.

Common Applications

Power Factor Correction

Capacitors are used in industrial and commercial settings to improve the power factor of electrical systems. By adding capacitors in parallel to inductive loads, the phase difference between voltage and current can be reduced, leading to more efficient energy use and reduced demand charges from utilities.

Smoothing Power Supply Output

In power supplies, capacitors are essential for smoothing out voltage fluctuations, converting the rectified AC output into a steady DC output. Large electrolytic capacitors are often used in this application to handle significant voltage variations.

Timing Circuits

Capacitors are integral to timing circuits, such as those found in oscillators and timers. By charging and discharging at predictable rates through resistors, capacitors can generate precise time delays and frequencies critical for the operation of various digital and analog circuits.

Safety Considerations

Voltage Rating

Capacitors have a maximum voltage rating that should not be exceeded to prevent breakdown of the dielectric and potential failure. Exceeding this rating can lead to overheating, leakage, or even explosion.

Polarity in Electrolytic Capacitors

Electrolytic capacitors are polarized, meaning they must be connected with the correct polarity. Reversing the polarity can cause the capacitor to fail, potentially resulting in a short circuit or explosion.

Discharge Precautions

Capacitors can retain a charge even after power is removed. It is crucial to discharge capacitors safely before handling or servicing electronic equipment to avoid electric shock.

Related Terms or Concepts

Dielectric

The insulating material between the plates of a capacitor, which increases its capacitance by reducing the electric field strength for a given charge.

Farad

The unit of capacitance in the International System of Units (SI), defined as one coulomb of charge per volt.

Inductor

A passive component that stores energy in a magnetic field, often used in conjunction with capacitors in resonant circuits to filter frequencies or store energy.

RC Circuit

A circuit composed of resistors and capacitors, commonly used for filtering, timing, and waveform shaping applications.