High School Physics

Capacitors and their usage

Capacitors and their usage is the topic of this post. The capacitor is a component that has the ability or “capacity” to store energy in the form of an electrical charge producing a potential difference across its plates. In other words, Capacitors are components of electrical circuits that temporarily store electric charge. Capacitors are simple passive devices.

Capacitors consist of two or more parallel conductive metal or foil plates that are not connected or touching each other but are electrically separated either by air or by some form of insulating material such as paper, mica, ceramic, or plastic and which is commonly called the capacitors Dielectric.

Capacitors and their usage

Brief History

Capacitors have been used to store electrical energy since the late 18th century. Benjamin Franklin was the first to coin the phrase “battery” for a series of capacitors in an energy store application.

Capacitor – definition

The capacitor is such an arrangement in which the capacitance of a conductor is increased by bringing another earthed conductor near to it. In fact, a capacitor is a pair of two conductors of any shape which are close to each other and have equal and opposite charges. These conductors are called plates of the capacitor.

[ Also read: Principle of capacitors]

The capacitance of a capacitor

If the charges on the plates of a capacitor are +Q and -Q and the potential difference between them be V, then the capacitance of the capacitor is given by C = Q/V.

Thus, the capacitance of a capacitor is defined as the ratio of the charge and the potential difference produced between the plates.

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[Also read: Capacitor & capacitance formulas

Also read Parallel plate Capacitor formula derivation]

Usage of capacitors

The addition of a capacitor into a circuit has two possible effects: either introducing a time delay into the circuit; or storing electrical energy for a short period of time.

A capacitor’s ability to become charged by a voltage and then hold that charge allows capacitors to be used in electrical and electronic circuits in a variety of ways, from smoothing out fluctuations in voltage power supply levels to timing and filter circuits when used in conjunction with a resistor.

Applications of capacitors – a few examples

(i) They are used in the ignition system of automobile engines to eliminate sparking.

(ii) They are used to reduce voltage fluctuations in power supplies and to increase the efficiency of power transmission.

(iii) Capacitors are used to generate electromagnetic oscillations and in tuning the radio circuits.

(iV) Capacitors provide a voltage boost, which cancels part of the drop caused by system loads. Switched capacitors can regulate voltage on a circuit. If applied properly and controlled, capacitors can significantly improve the performance of distribution circuits. Capacitors oppose changes in voltage. It takes time to fill up the plates with charge, and once charged, it takes time to discharge the voltage.

v) Production of low voltage DC power supply from Mains to power the circuit – The conventional method is the use of a step-down transformer to reduce the 230 V AC to the desired level of low voltage AC. The most simple, space-saving, and low-cost method is the use of a Voltage Dropping Capacitor in series with the phase line.

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vi) Capacitors for Energy Storage – large capacitors are included in the car audio systems to provide extra power to amplifiers when needed.

Vii) Capacitors for Power Conditioning – One important application of capacitors is the conditioning of power supplies. Capacitors allow AC signals to pass but block DC signals when they are charged. They can effectively split these two signal types, cleaning the supply of power.

This effect has been exploited to separate or decouple different parts of electrical circuits to reduce noise which could lead to a reduction in efficiency. Capacitors are also used in utility substations to counteract inductive loading introduced by transmission lines.

Viii) Capacitors as Sensors – Capacitors are used as sensors to measure a variety of things, including air humidity, fuel levels and mechanical strain. The capacitance of a device is dependent on its structure. Changes in the structure can be measured as a loss or gain of capacitance.

ix) Capacitors in computer memory – Capacitors have found increasingly advanced applications in information technology. Dynamic Random Access Memory (DRAM) devices use capacitors to represent binary information as bits. The device reads one value when the capacitor is charged and another when discharged.

x) Capacitive Touch Screens -With a touch screen, such as on a smartphone or tablet, just by simply touching an icon we can immediately access an application.

xi) Defibrillator – application of Capacitors in the medical field.

xii) camera’s flash unit also uses a capacitor.


Capacitors are a basic component of electronics and have a host of various applications. The most common use for capacitors is energy storage. Additional uses include power conditioning, signal coupling or decoupling, electronic noise filtering, and remote sensing. Because of their varied applications, capacitors are used in a wide range of industries and have become a vital part of everyday life.

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