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Capacitor Tutorial Summary

Capacitor Tutorial Summary

A capacitor consists of two metal plates separated by a dielectric

As we will see in this capacitor tutorial, Capacitors are energy storage devices which have the ability to store an electrical charge across its plates. Thus capacitors store energy as a result of their ability to store charge and an ideal capacitor would not loose its stored energy.

The simplest construction of a capacitor is by using two parallel conducting metal plates separated through a distance by an insulating material. This insulating material is called the “dielectric”. the dielectric plays an important role in the electrical operation of a capacitor and for this capacitor tutorial we can summarise the main points below.

  • A capacitor consists of two metal plates separated by a dielectric.
  • The dielectric can be made of many insulating materials such as air, glass, paper, plastic etc.
  • A capacitor is capable of storing electrical charge and energy.
  • The higher the value of capacitance, the more charge the capacitor can store.
  • The larger the area of the plates or the smaller their separation the more charge the capacitor can store.
  • A capacitor is said to be “Fully Charged” when the voltage across its plates equals the supply voltage.
  • The symbol for electrical charge is Q and its unit is the Coulomb.
  • Electrolytic capacitors are polarized. They have a +ve and a -ve terminal.
  • Capacitance is measured in Farads, which is a very large unit so micro-FaradμF ), nano-FaradnF ) and pico-FaradpF ) are generally used.
  • Capacitors that are daisy chained together in a line are said to be connected in Series.
  • Capacitors that have both of their respective terminals connected to each terminal of another capacitor are said to be connected in Parallel.
  • Parallel connected capacitors have a common supply voltage across them.
  • Series connected capacitors have a common current flowing through them.
  • Capacitive reactance, XC is the opposition to current flow in AC circuits.
  • In AC capacitive circuits the voltage “lags” the current by 90o.

The basic construction and symbol for a parallel plate capacitor is given as:

capacitor tutorial the symbol

49 Comments

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  • Rahul Behera

    Electronics All Projects

  • sharath kumar H

    I need capacitor design and working principle indepth including the role of capacitors in bridge rectifiers ,filters and also need of cycloconverters

  • Johnny

    Superior tutorial right to th e point. And easy to understand

  • INNOCENT AKERA

    VERY ORGANISED NOTE

  • Jeremiah

    explaination in your web side is very nice so thank you so much.

  • Filipe Jorge Silva

    What is the material for build the plates?

  • Manjeet prejapat

    Construction and charactereristics of capactions for electronics circuit

  • Veneswaila

    LGBT

  • Mildret

    The construction of a capacitor was found very simple . Thanks

  • Shafii

    Very helpfully

  • Rahil

    Types of capacitors

  • Arwa Hashmi

    A very good article. Helped me out.

  • david moccia

    My fan has a 3 speed 5 wire capacitor with ratings of 3.5/4.5/4.5 microfarads: if a capacitor has higher ratings, say 5/5/5 will that work well as a replacement or do the microfarads ratings need to be less than 3.5/4.5/4.5, say 3/3/3, in order for it to work as a replacement capacitor?

    • Wayne Storr

      Fan motors can have different windings or tappings for speed control in which series connected capacitors are used to insert a phase shift between the start and run windings. Changing the capacitor value may result in the fan motor running slowly or not at all for the different speeds. Changing the capacitors to all the same values may result in the motor operating at the same rotational speed for all speed selections.

      • Dave

        Thanks. After calling the fan company and finding out that a replacement capacitor was going to cost me $22 I decided it wasn’t worth it since it is an older fan and I was planning to sell it anyway.

  • 189103 Premarathna A.M.N.S.

    very helpfully.thank you

  • Raj Singh

    Hello all, m new at this things on capacitors but do have some knowledge on the functioning of them, my ? Is I removed a capacitor , polarized with 25v and 470 uf , can replace it with a 25v with 2200uf or will it defeat the purpose , tanks

  • aj

    hi 🙂

    i am new in electronics.
    i have bought a device (esr) which is showing me two results:
    1. uf=653, and
    2. c=12pF

    how can i, by these results estimate the capacitor? another words, what these numbers means to me?

    sincerely,
    ( – ) aj

  • Nithin

    Sir, could you please explain ,
    What is the actual practical meaning of current leads voltage by 90 degree in AC capacitor.

    • prince

      The major reason for denoting 90 degree is overall instantaneous power in the capacitor is zero(which means it cannot practically store charge for infinite time).

      One more reasoning is capacitor conducts due to flow of charge which means when you supply a current +Q develops

    • Sunil Kumar KR

      When a capacitor is connected across a source it observed electrical energy and store it in the form of electrostatic energy. This is because of the accumulation of positive ions on the plates connected to the positive side of the source and negative ions on the side of the capacitor connected to negative side of the source. Moment of any charge can be considered as flow of current. it means when a capacitor is connected across a voltage source and current flows from the voltage source to the capacitor plates does accumulating charge on capacitor plates connected to positive and negative sides of the voltage source. Due to the accumulation of charges the voltage across the capacitor gradually increases until it becomes equal to the voltage source. Then the current becomes zero. if you want a very simple answer to your question it will be as follows:

      when a capacitor is connected across a voltage source first a current is established which in turn accumulates charges on the capacitor which gradually increases the voltage across the capacitor. Inshorts voltage follows the current.

  • Malshan Ranawella

    You’ve done a really great job on explaining everything in this website. Thank you very much. I recommended many colleagues this page because of its simplicity.
    Here’s another small request from me.
    I think the fact that why AC currents pass through capacitors should be explained more with diagrams.
    Other than that, please include the role of capacitors in Diode Clamping Circuits and Voltage Doubler and Tripler circuits.

  • Stemmere

    I hardly understand capacitor and capacitance

  • Bernardo Donato

    I have a incent question.
    I hear a technician say that a wash machine capacitor. The higher microfarat the higher the rpm. Is that version correct ?
    Thank you in advance for help
    Regards
    Donato