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Wednesday, August 19, 2009

What is Electric Circuit?

Last time we have a little review of basic Physics. The reason why I included those topics here in Electrical Engineering as a beginning topic because those topics are mostly given in the board exam during our time. Please bear with me for three times posting for I have to do a little SEO for this blog. The reason why I'm doing this is to drive more traffic to this site. I was currently standing number 6 for a keyword Electrical Engineering for Beginners for which this site is really intended to.

Anyway, let's begin with our new topic for today. This is already the start of our major discussion where every detail should be understand by everyone.

The Electric Circuits

Since we will be dealing with electric circuit starting today up to the rest of the topic, it is recommended that you should have an accurate picture of what electric circuit is and how the electric current behaves on it.

Just recall for a moment what we had reviewed on our previous topic about the current flow on Voltage, Current, Power and Energy. You have learned that if you connect a length of wire or a conductor across the positive and negative terminals of a source of electromotive force ( emf) let say, a battery, the potential difference (voltage) makes the current flow and also that electrical energy is needed to keep the current flowing.

Any combination of a conductor and a source of electricity connected together to permit the electrons to travel around a continuos stream is called electric circuits. The figure shown below is a simple electric circuit that we are talking about ( you may click the image to enlarge)

Many millions of free electrons that have already been separated from the outer orbits of their respective atoms by the heat of room temperature, and which have been wandering aimlessly in all directions through the wire, now come under a common controlling force. They repelled by the more negative ( or less positive) charge which have been set-up at one end of the wire, and strongly attracted by the less negative (or more positive) charge which have been connected at the other end. This movement are converted into a disciplined current flow from more negative to more positive, and the electric current flows.

Take note that electrons are negative charges of electricity and have practically no weight at all. It only means that when a potential difference is applied to the wire, they respond to it immediately. Likewise, when the potential difference is removed, the electrons stop their disciplined flow in a single direction at once and resume their wanderings through the conductor material.


What are the conditions required in order to maintain the flow of an electric current in a circuit? Please take note of these conditions. They are simple but very important when it comes to actual application.

1. There must be a source of potential difference or voltage to provide the energy which forces electrons to move in a disciplined way in a specific direction.

2. There must be continous (complete) external path for the electrons to flow from negative terminal to the positive terminal of the source of voltage.

We have mentioned about external path. This is usually made up of two parts: the conductors or the wires, and the load to which the electric power is to be delivered for some useful effects. In the above illustration given, the lamp or the small bulb is load in the given sample.

An electric circuit is thus completed its electrical pathway, consisting of not only a conductor in which the current will flow (negative to positive), but also of a path through a source of potential difference from positive back to negative.

A small bulb connected across a dry cell is an example of electric circuit. Current flows from the negative (-) terminal of the cell, through the small bulb (the load), to the positive terminal. The action of the cell is that it provides a regenerative path for the flow of electrons to be maintained.

As long as this electrical pathway remains unbroken at any point, it is a closed circuit and the current flows. But if the pathway is broken, it becomes an open circuit and no current flows.

An Open Circuit

A Closed Circuit

This is how the Electric Circuit is defined. On my next post, I will going to differentiate about DC and AC Circuits. We should be able to comprehend well the difference between the two. We will be discussing it separately on our course outline for they have completely separate ideas. I would like to organize my ideas and lessons presented in this Electrical Engineering site.

I hope you enjoy with this simple discussion today. I'll be back shortly.



Team Bolivia said...

Hi Donny,
Thanks so much for this site. I am a electronics technologist living in Bolivia for a year teaching english and other things to kids who live in poverty here. They have asked me to put together some vocational training for some teens on Electricity but I didn't have any content. If you don't mind I will use some of your blog to teach them some of the basics of electronics...in Spanish of course. Thanks so much for pulling this together and God Bless,

Anonymous said...


Anonymous said...

Thanks you very much. Your explanation help me a lot comprehending what is an open and a close electric circuit.

Wish you well,


Unknown said...

Thank you so much Erick. I seldom update this blog because I'm just posting it in a free hosted. I still finding ways to make my own website so that I could post and own my contents.

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