Today, I will be introducing this great topic useful for engineers particularly electrical engineering student. Electricity is the life we can't do without it. Have you ever see a person that said he don't need electricity? So electrical engineers are illuminance of the world.

>"Electrical science has revealed to us the true nature of light, has provided us with innumerable appliances and instruments of precision and has thereby vastly added to the exactness of our knowledge" Nikola Tesla

Let's start with definitions of some terms.

What is an electric circuit?

An electric circuit is simply a closed path through which an electric current flows.

This is a simple circuit diagram below,

[IMAGE: https://cdn.steemitimages.com/DQmeHaBPpMZjYH4MCN8RXb4PB4YFs9M1CpHDHcj4jcwsECT/s_electriccircuit.png]
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Electric current (I)

Electric current (I) is a flow of electric charge. This charge can be carried by electrons in wire and ion in an electrolyte.

[IMAGE: https://cdn.steemitimages.com/DQmdViVcGt1HApXapdsxyb6atzgfJFSm4vyxeAswH1qbhqQ/dcp1b.gif]
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The Standard International SI unit for measuring an electric current is the ampere and it is denoted with A, which is the flow of electric charge across a surface at the rate of one coulomb per second. Electric current is measured using a measuring device called an ammeter.

Electric current is divided into two part which is Direct current (D.C) and Alternating current (A.C).

Let's discuss briefly on the two parts one another.

Direct current D.C

Direct current is the flow of charge moving in one direction.

[IMAGE: https://cdn.steemitimages.com/DQmUtG1Hp6Z3iACRysaJY5XzaZjao4RAcneCLFp3Gt4squi/DC-Source%20(1).png]
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The source of a direct current is produced by batteries, electrochemical, and photovoltaic cells. And it is rechargeable. A typical example of DC is a phone battery because it is rechargeable.

Alternating current.

Alternating current is the flow of charge moving in sinusoidal form or changes directions periodically.

[IMAGE: https://cdn.steemitimages.com/DQmd5knTyZSMyTFPBDPHZfRNWBqaq9XVkH23S772jaR9NfX/AC-Source.png]
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The main difference between A.C and D.C is thatA.C is not rechargeable while D.C is Rechargeable. Outlets at home or offices are using A.C because the appliances will be automatically switched off when there is no power supply.

I believed you have to know the difference between A.C and D.C now.

Resistance

Resistance is the opposition to the flow of electric current.

The standard International SI unit is Ohms, which is denoted with Ω. The circuit components that perform this task is called a resistor.

[IMAGE: https://cdn.steemitimages.com/DQmU4DaJArpzn2ENBJXyFTEgZ9djxFaCqNe197LNEdSD6Eq/dcp1d.gif]
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From the picture above, you can see that there are three types of the resistor which are fixed value resistor,variable resistor and light dependent resistor.
Let's briefly discuss the three types,

• Fixed value resistor :-this is a resistor cannot be changed as it is set at a specific value.
• Variable resistor:- this is a resistor that its value can be adjusted.
• Light-dependent resistor:- this is a resistor that has a resistance that changes with the light intensity that falls upon it. It is also called photoresistor.

References

Electronic tutorial-DC circuit theory
Elprocus- Ac and Dc

The sub-topic I will be writing about in my next posts are listed below.

> * Ohm's law
> Series and parallel circuits
> Voltage and current divider rule.
>* DC circuit analysis

Feel free to ask questions if don't understand something on the tutorial.

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