WHAT YOU NEED TO KNOW ABOUT CAPACITORS (in simple terms)…

sistem (60)in #steemstem • 8 years ago (edited)

Hello steemians, it’s a beautiful day today and I am here once again with yet another educative topic which though not everyone can relate with, but as usual, I will try my best to carry everyone along and make this as practical as possible.

Today we will be looking at the CAPACITORS and I will be telling you virtually everything you need to know about capacitors.

I am pretty sure many of us already know what capacitors are and are very familiar with it while many of us have no idea and would probably be hearing about it for the first time ( For the non-science inclined and non-electrically inclined individuals among us). Well, no worries as I make to bring to your knowledge what a capacitor.

Below is a picture showing different capacitors...

image source

What are capacitors?

A capacitor is a passive electrical component with two terminals which stores potential energy in an electric field. By passive, I mean a component that consumes but doesn’t produce energy and an electric circuit which consists of only passive component is called a passive circuit and would have exactly the same properties of a passive component. The opposite of a passive component is an active component.

The effect of a capacitor in an electrical circuit is called Capacitance which will be discussed in detail shortly. A capacitor is basically designed to add capacitance to an electrical circuit and this capacitance exists between two electrical conductors in close proximity in a circuit. Capacitors were originally Known as condensers and they are component.

Capacitors are widely used in so many electronic devices and they vary in shapes, sizes and types. Most of the capacitors contain electrical conductors which are often in the form of metallic plates separated by a dielectric medium. The metallic conductor may be a foil, thin film, sintered bead of metal, or even an electrolyte (Liquid metal). Dieletrics will be discussed shortly so don’t start getting confused already. Remember I promised to carry you along, so you have nothing to worry about. Just walk with me (SMLIES).

When talking about capacitors, two words always comes to mind which I would like to discuss now as promised so we can have a better understand about the terms used here. These words are;

Dielectric
Capacitance

What are dielectrics?

Dielectrics are substances that have very poor electrical conductivity but effectively support electrostatic fields. The non-conducting dielectrics acts to increase the capacitor's charge capacity i.e the capacitor’s ability to store charges. In practice, most dielectric materials are solid. Examples include porcelain (ceramic), mica, glass, plastics, and the oxides of various metals. Dielectric materials are not limited to just solids though as some liquids and gasses can also serve as good dielectric materials. Funny enough, dry are is also an excellent dielectric and is used in making variable capacitors which is used as a component in the manufacture of radios. Variable capacitors in radios are used in frequency tuning.

Whenever you are searching for a “channel” or frequency in your local radio which made with a tuning knob, just know that the actual component which works and aids in the frequency selection is the variable capacitor.

Distilled water is also a fair dielectric and a vacuum is an exceptionally efficient dielectric. These materials are all non-conductive but have the ability to store up electrostatic charges.

image source : Position of the dielectric in a ceramic capacitor

An important property of a dielectric is its ability to support an electrostatic field while dissipating minimal energy in the form of heat. The lower the dielectric loss, the more effective is a dielectric material.

Another important consideration is the dielectric constant. This is the extent to which a substance concentrates the electrostatic lines of flux. Substances with a low dielectric constant include a perfect vacuum, dry air, and most pure, dry gases such as helium and nitrogen. Materials with moderate dielectric constants include ceramics, distilled water, paper, mica, polyethylene, and glass. the material that has a very high dielectric constant is Metal Oxide meaning that it concentrates the electrostatic lines of flux better that the rest.

Now, what is capacitance?

Capacitance is the ability of a body to store an electric charge. These are two basic types f capacitance;

Self Capacitance: Any object that can be electrically charged is known to exhibit self-capacitance and a material with a large self-capacitance holds more electric charge at a given voltage than one with a low capacitance.

Mutual Capacitance: Mutual capacitance occurs when two charge holding objects or conductors come in close proximity in which current passing through one of the conductors passes into the other. This could be intentionally or unintentionally done. In transmission lines, when conductors are closely spaced together, the air or material separating the lines acts as a dielectric, and the conductors act as capacitor plates exhibiting what is known as mutual capacitance.

image source: Mutual capacitance

Capacitance is defined as the ratio of the electric charge on each conductor to the potential difference between them. The unit of capacitance in the International System of Units (SI) is the farad (F), defined as one coulomb per volt (1 C/V). Capacitance values of typical capacitors for use in general electronics range from about 1 picofarad (pF) (10−12 F) to about 1 millifarad (mF) (10−3 F).

The capacitance of a capacitor is proportional to the surface area of the plates (conductors) and inversely related to the gap between them. In practice, the dielectric between the plates passes a small amount of leakage current. It has an electric field strength limit, known as the breakdown voltage. This breakdown voltage is the maximum voltage which will be passed through the capacitor dielectric before it loses its capacitance.

Brief history of capacitors…

Actually, there has been a little bit of confusion o who really invented the capacitor. In November 1745, a German scientist named Ewald Georg Von Kleist was said to have invented the capacitor. Several months later, a Dutch professor at the university of Leyden, Pieter Van Musschenbroekcame up with a similar device and called it the Leyden Jar, which was credited as the first capacitor. Unfortunately, Kleist had no detailed records or notes to his invention and so he was often overlooked and was not regarded as a contributor to the invention but as time went on and years past, people started giving credit to him as I was established that their research was independent of each other and merely a scientific coincidence.

image source: Left(The layden Jar)
image source: Right(The cross section of the Layden Jar)

Many years passed ad a scientist called Benjamine Franklin decided to work with the Leyden jar in his experiment with electricity and found out that a piece of flat glass worked just like the jar model and so it prompted him to develop the first Flat capacitor.

After years again, an English Chemist called Micheal Faraday pioneered the first practical application of the capacitor when he tried storing unused electrons in his experiments. This led to the invention of the first usable capacitor made from large oil barrels. Faradays progress with the capacitor is actually what enabled us to deliver power over great distances and as a result of his achievements in the field of electricity, the unit of measuring capacitance became known as the Farad.

Now that’s how the capacitor we know today came to be and I hope I have added to your knowledge today …LOLZZ

Types of capacitors

There are so many types of capacitors but not all can be listed here. I will be listing the very important ones and they are;

CERAMIC CAPACITORS : Ceramic capacitors are made using ceramic dielectrics and that’s where the name ceramic capacitor comes from. Though there are different types of ceramic capacitors, but all ceramic capacitors are known for their low loss factor and reasonable level of stability.

image source: Ceramic capacitor

They do not give a high level of capacitance though and so ceramic capacitors are typically rated in picofarads (pF). They are also not polarized, meaning that they do not have a designated positive and negative terminal.

ELECTROLYTIC CAPACITORS : These capacitors are polarized capacitors which means they can only be placed a certain way in the circuit and if placed otherwise would lead to the explosion of the capacitor. They are often rated with given voltage and it is advised that you work below the rated voltage because any voltage higher than the given/rated voltage would lead to the damage of the capacitor.

image source: Electrolytic capacitor

Electrolytic capacitors are known to be rated with values greater than 1 microfarad because of their high level of capacitance per unit volume. These capacitors have a wide range of tolerance ranging from -50% to +100% but do not operate well at high frequencies ranging from 50-100 KHz.

PLASTIC FILM CAPACITORS : These are non-polarised capacitors and they can be used for a variety of purposes. They perform at high frequencies but are lower when compaied with the ceramic capacitors. The dielectric used in this capacitor is the Plastic film as the name implies which may include Polycarbonates, Polyesters***, Polystyrenes e.t.c. They are often rated in picofarads (pF).

image source: Plastic film capacitor
TANTALUM CAPACITORS : These are polarized capacitors and are most times used in place of the electrolytic capacitor because of their small size. Just like the aluminium electrolytic capacitor, they have zero tolerance to being revers biased (placing the polarities wrongly) and so would explode if you do so.

image source: Tantalum capacitor

The only reason many still make use of the electrolytic capacitors over the tantalum capacitor is due to their low voltage ratings. The maximum voltage a tantalum capacitor can handle is 35V while an electrolytic capacitor can handle voltages way higher than that.

MICA CAPACITORS : Mica capacitors are a group of unpolarised capacitors. The dielectric used is the mica film which gives credence to the name. However, they have very low capacitance and are usually rated in thousands of picofarads (pF). They are not often used these days, but if high level of stability is needed then you would like to go for the mica capacitor because they have a very high level of stability.

image source: Mica capacitor
SUPERCAP CAPACITORS : These capacitors are large polarised capacitors and are often used for applications like memory hold up and basically anything that has to do with memory. They have very high capacitance rating of about 1 farad and above although their frequency response is very low ad so can’t be used for high frequency devices meaning that they have low stability.

image source: Super capacitor

To drive the application of this capacitor home, am sure many of us have experienced a situation where you switch a Compact Fluorescent Lamp (CFL) off and the light stays on for a while before going off, well this is the capacitor responsible for that. They are also used in time delay equipment due to their memory storing ability.

CONCLUSION…

Capacitors are widely used in the construction of electrical appliances and many of them are applied for different functions. That is why you can find different capacitors in a single appliance.

If you read through the types of capacitors listed above, you would have noticed a trend, it you were observant enough. You would have noticed that the higher the capacitance of a capacitor, the lower its stability. This is something I never knew until when I took out the time to do this research and so even if you did not learn anything today, let this be your take home (SMILESSS).