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Insight - How Capacitor works

Written By: 

Ashok Sharma


Capacitor is a widely used electronic component. It stores electric charge and then discharges it into the circuit. It blocks the direct current and allows the alternating current to pass through it. Depending on the purpose, there are a variety of capacitors being used like ceramic, electrolytic, mylar, mica, etc. We will explore an electrolytic capacitor through this article.

Structure of a Capacitor: A capacitor contains two conductor plates which are generally made of metal and an insulator between them. This insulator also known as dielectric is made up of material like paper, plastic, ceramic or glass. The two plates are electrically connected to the external circuit with the help of two thin metal rods also known as the legs of the capacitor.
These two plates are used to store charge between them. One is connected with positive voltage and other one with negative voltage. A capacitor is characterized by the parameter capacitance. Capacitance is measured as ratio of difference of charges between the plates and total voltage drop between the plates.
C = dQ/dV
The unit of capacitance is FARAD.
Let’s have a closer look into the structure and how a capacitor is able to store charge
Electrolyte Capacitor
Fig. 1: Commonly used Simple Electrolytic Capacitor
The above image shows a simple electrolytic capacitor with two thin rods coming out from the cylindrical container. The capacitor is wrapped up using a plastic covering. This covering is done to label the capacitor.

Metal Container 

Capacitor metal container and label
Fig. 2: Outer Casing of Electrolytic Capacitor with Labeled Plastic Covering
On removing the label, you can see a metal container adjoined with a rubber stand to hold the entire setup.

Internal Structure

Capacitor Internal Structure
Fig. 3: Internal Structure of Metal Container in Electrolytics Capacitor
Inside the metal case is a folded layer of dielectric in between metal plates. Next images give a clear perception of the internal structure of the capacitor.


Inside a Capacitor
Fig. 4: Closer View of Dielectric Arrangement in metal Container of Electrolytics Capacitor
In the above image, we can clearly see two different types of layers, folded like a swiss roll. A dielectric layer is sandwiched between two metal plates. These metal plates are used to store charge and the dielectric works as an insulator between them. These plates are folded round to minimize the size of the capacitor.
One plate works as cathode and another as anode.  To increase the value of a capacitor and the same time to keep the size smaller, we use electrolyte. However depending on the size and application, there are different types of electrolytes used in different ways within a capacitor.Generally, anode is soaked into liquid  electrolyte to increase the surface area of the plate as well as efficiency.

Metal Electrodes

Unfolding these plates brings us even closer to the internal architecture of the Capacitor.
Capacitor Metal Electrodes
Fig. 5: Internal Architechure of Electrolytic Capacitor
Now, you can see that the plates are directly connected to the legs of capacitor and a rubber stand is used to hold these plates.

Capacitor Plates

Fig. 6: Complete Assembly of Electrolytic Capacitor with Plates and Metal Electrodes

Lastly to summarize the building block of a capacitor includes a pair of metal plates, thin rods, a dielectric, a rubber stand, a metal container and a plastic covering.

Formation of a Capacitor, Parts of a capacitor

Fig. 7: Overview of all Parts in Simple Electrolytic Capacitor



amazing, first time i have seen the capacitor so clearly and its fabrication...........................

awesome !!!

great work


Assalamualaikum guys...I m using ultrasonic sensor to make velocity counter...can any one tell me how to use ultrasonic sensor...plsssss..i don't have any information about this sensor...

thi is vey use full for the lerners

why because  its very interesting

 like a cinema

respected sir,

Pls send insite of resistor,transformer,diode,transistor,IC,SCR,LED,UJT,FET,MOSFET


realy amazing

my request to add more like how resistors, inductors etc.,, manufactured.

but really its outstanding.

great work..


article is so much interesting and knolegeble.

acha hain ..............can u tell me mr ashok what is the funtion and usage of paper capacior



really amazing!!!!

awesome brooo ..... nice approach to give a pictorial view of the capacitor... U ROCKcool


can u please demystify the pattren of charging and discharging for ac as well as dc voltages..




its just great ,,, really informable,,, can you please put this kind of info of all the component as it will be great to understand in this way,,,,,,smiley

cool ...small.. structure../


great .. could you say where and all to use this capacitor .. because i am seeing this in various places


ur site infos r just mindblowing, d way u show d composition inside!!!Pls also put insite of resistor,transformer,diode,transistor,IC,SCR,LED,UJT,FET etc it wil b really of gr8 help :)

sir can u explain how it store charge in it?


sir can u pls explain how it store charge in it?

superb website for begineers

It is really helpful for the beginners.


It will be useful for anyone. there are different types of capaciter,How we know which type capaciter use  in particular circuits


Outstanding post, you have pointed out some excellent details, I as well conceive
this is a very great website.