STARTING WITH BEN FRANKLIN

Many people think Benjamin Franklin discovered electricity with his famous kite-flying experiments in 1752, but electricity was not discovered all at once. At first, electricity was associated with light. People wanted a cheap and safe way to light their homes, and scientists thought electricity might be a way.

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Potential Difference (Voltage)

Imagine that in you decided to spend your next week-end in himalaya mountains (it's very cold there ,is't it ? ) with your friends and an Avalanche is occurred (ohhh action film) , have you asked your self why this ball of ice take its way to the earth , of course it have a potential energy resulted from height due to gravitational force .

The same thing happened in electronics , free electrons moves in high speed resulting beam ogf electrons (current) due to potential difference but this potential differ is't for height it's for positive ions (holes) , in other word in region there are a lot of electrons and another there are low no. of electrons . free electrons moves from regions fulled with free electrons to low one , this is so-called Voltage or potential difference (really it's natural laws , isn't it ) .

In other hand , you can say that the voltage is the pressure needed to move electrons from one point to another , and also we can say that current is a result from difference in potential (voltage) .

Finally , voltage is needed , current is resulted , but we forget to say that voltage can be measured by a unit called "volt" (it is named in honor of the Italian physicist Alessandro Volta (1745–1827), who invented the voltaic pile ) .

Really now we can call voltage by voltage or electrical potential difference or electro-motive force .

Note plz don't forget to watch videos in my blog about this principles Click Here , Pling heheheh

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A CURRENT BEGAN

Before swimming in electronics components world , we need first to know about some basics for what we can understanding electricity .

what about Electric Current

electrons is a very small bodies (have you ever seen an electron moving through the street ) that spins in a very high speed around nucleus , electrons is a negative charged bodies that attached with positive one (the terms negative and positive is is an arbitrary terms two describe the two types of forces )called protons , but we can't forget that nucleus made of two bodies protons and neutrons (according to neutral charged bodies) .

And all previous is the structure of so-called "atom" (Protons And neutrons in nucleus attached with electrons ) , any structure of any material is made of millions of atoms (can you imagine # of atoms in the whole world ).

when this electrons is at rest called a " Charge" , the charge is made of 6.24 followed with 18 zero of electrons (you can note that this charge is measured with coulomb One coulomb is the amount of electric charge transported in one second by a steady current of one ampere () ,It is named after "Charles-Augustin de Coulomb" ) .

If this charge is moved with time this is called An Electrical current "I" (I=dq\dt) , in other hand any continuing flow of charged particles is called current , current can be measured by ampere (It is named after André-Marie Ampère (1775–1836), French mathematician and physicist, considered the father of electrodynamics. In practice, its name is often shortened to amp ) .

We can note that we are studying electronic brance (electronic components)

in order to control this beam of electrons (current) , for example changing its direction or its frequency and so on .

Now let's start to define "Amp" , if this no. of electrons (charge) is is moved through certain point in one second of time it will create an electrical current of one amp (1 amp = 1Coulomb/1 sec ) .

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Useful Quantities

Notes in electronics we use very small ranges of current and voltages , follow is list of this ranges .

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How to Desolder Electronic Parts

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Mechatronic car

Click " Read more... " to see video..............

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Resistance And Resistor (Part # One)

Before we know about our first component in electronics "Resistors" , we need to know more and more about ohm's circuital law and types of materials .

Understanding Ohm's Law (the most simple and important law in circuits ) :

ohm has been discovered that the voltage and current(discussed previously) related together , he found that when the current of electrons increases , this mean that it need more voltage to increase.

Ohm's Law defines the relationships between voltage and current , current is changed proportionally with voltage , this mean that the relationship between "V" and "I" is linear relationship and the slope of this curve is so-called "Resistance" (note that resistance is an example for linearity relation ship between volt and current , but for example a diode is an example for non linear relationship between this two variables as we will see soon ) .

Now we can define ohm's law , Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference or voltage across the two points, and inversely proportional to theresistance between them, provided that the temperature remains constant.

The mathematical equation that

describes this relationship is :

From this equation , we can we can conclude that when resistance increases this mean that more current will produced and as a result we need more voltage to produce this current .

Also from ahm's law : V=IR

the voltage that we need to apply to move electrons from one point to anthor is equal to flow of electrons that i need to move it multiply wthi the ratio of the resistance that will resist it ( And also for current I=V/R and Resiatnce R=V/I ,Plz disscuss it with yourself)

Ohm Triangle :

Ohm's Law is a very simple and useful tool for analyzing electric circuits. It is used so often in the study of electricity and electronics that it needs to be committed to memory by the serious student. For those who are not yet comfortable with algebra, there's a trick to remembering how to solve for any one quantity, given the other two. First, arrange the letters E, I, and R in a triangle ,If you know E and I, and wish to determine R, just eliminate R from the picture and see what's left, etc.

Note : ohm's low is relate the three variables "V" , "I" and "R" with Power , Let's see :

But , what about a "Resistance" :

definition :

The electrical resistance of an object is a measure of its opposition to the passage of a steady electric current (like friction in mechanics ) .

Resistance is measured in ohms (referred to Georg Ohm ) , the symbol for ohm is an omega Ω .

Resistance of an Conductor :

The resistance R of a conductor of uniform cross section can be computed as

where

: is the length of the conductor, measured in metres [m]

A : is the cross-sectional area of the current flow, measured in square metres [m²]

ρ : is the electrical resistivity (also called specific electrical resistance) of the material, measured in Ohm · metre (Ω m). Resistivity is a measure of the material's ability to oppose electric current.

But let's understand this equation :

For Example In metal wire, there are a number of atoms and free moving electrons. Electricity is the movement of these electrons through the wire. Resistance is caused when the free electrons moving through the wire collide with the atoms making their path through the wire more difficult. This means that if there are more atoms in the way to collide with the free electrons the resistance is increased. In a length of wire there will be a number of atoms, and in a wire twice the length, there will be twice the number of atoms. In turn this will lead to there being double the number of collisions between the electrons and the atoms increasing the

resistance by 2 . ( the idea of the free moving electrons being resisted by the atoms in the wire , the more the atoms in the way the more the resistance produced , also by this way with

ρ and

A )

electrons moving through the wire collide with the atoms in it

to watch the full video press here # 2 Pling hehehe

Resistance Types :

1. fixed resistance

2. variable resistance

Conclusion :

An electric circuit is formed when a conductive path is created to allow free electrons to continuously move. This continuous movement of free electrons through the conductors of a circuit is called a current, and it is often referred to in terms of "flow,"(Another Example: just like the flow of a liquid through a hollow pipe) .

The force motivating electrons to "flow" in a circuit is called voltage. Voltage is a specific measure of potential energy that is always relative between two points. When we speak of a certain amount of voltage being present in a circuit, we are referring to the measurement of how much potential energy exists to move electrons from one particular point in that circuit to another particular point. Without reference to two particular points, the term "voltage" has no meaning.

Free electrons tend to move through conductors with some degree of friction, or opposition to motion. This opposition to motion is more properly called resistance. The amount of current in a circuit depends on the amount of voltage available to motivate the electrons, and also the amount of resistance in the circuit to oppose electron flow. Just like voltage, resistance is a quantity relative between two points. For this reason, the quantities of voltage and resistance are often stated as being "between" or "across" two points in a circuit .

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An examples For More Understanding ohm's law

we study ohm's law and we said that it is a relation between "V","I" and "R" :

Let's see how these equations might work to help us analyze simple circuits :

In the above circuit, there is only one source of voltage (the battery, on the left) and only one source of resistance to current (the lamp, on the right). This makes it very easy to apply Ohm's Law. If we know the values of any two of the three quantities (voltage, current, and resistance) in this circuit, we can use Ohm's Law to determine the third.

In this first example, we will calculate the amount of current (I) in a circuit, given values of voltage (E) and resistance (R) :

What is the amount of current (I) in this circuit ?

In this second example, we will calculate the amount of resistance (R) in a circuit, given values of voltage (E) and current (I) :

What is the amount of resistance (R) offered by the lamp ?

In the last example, we will calculate the amount of voltage supplied by a battery, given values of current (I) and resistance (R):

What is the amount of voltage provided by the battery ?

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Resistance And Resistor (Part # Two: Let's start to buy our first component))

Before taking about ,what is resistors and how to you it and more .....

We need first to take in types of material

Types of material according to its electrical conductivity:

1. Conducting materials

in this type of material , the conductivity is high and have low resistivity such as metal as a general example.

2. Non-Conducting materials (Low Conductors and insulators)

in this type the opposite thing will be , it has law conductivity and low resistivity such as wood .

3. intermediate Conductive materials (Semi Conductors)

we won't to talk in it now

but , why does the conducting material has high conductivity , and low conducting material has low one ?

conductivity can be measured by free electrons in outer orbits in metal , the more the free electrons the more the current and low resistance (form ohm's law I=V/R) .

in high conducting materials , there are higher nombers of electrons than the lower one ( oh natural laws # 2) , this will cause higher resistance of low conducting material than high conducting materials .

From Now , we will divide our topic into two sections

1. Defining the " Resistor"

2. Some from Practical .

Section # 1 : Defining What is "Resistor"

after defining the "Resistance" , what do you think the resistor is ?

Resistor : is an electrical component that resist the current passing through it by producing voltage @ its terminals proportionally related with this current , so we can control current or voltage .

What is the Difference between "Resistance" and "Resistor" ?

resistance: the action of opposing the current (any conductor have a resistance)

resistor : an electrical component which has a certain resistance (we can say : this resistor has a resistance of ........ )

we can conclude this by , we put a a specific (constant) resistors as an electrical components to make some reistance in the circuit , in order to control current and voltage according to ohm's law .

For more understanding (English language lesson)

Resistance is a Noun that describes the naturals of the materials , but Resistors is an actor of an action (by by adding th "OR" prefix in the end of the verb "Resist" we will have "Resist-or" (Resist+or=Resist-or) for example "Visit-or .......etc.")

Note : When it comes actual circuit designing, dealing with components or physical board designing, these two words become interchangeable.

For example, if you say "a resistor of 22 ohms" or you say "a resistance of 22 ohms" both are acceptable.

Resistors electrical symbol:

Examples of Resistors :

Note : resistors also can be measured by the power that can dissipate from circuit in the shape of heat , and the power dissipated cab be calaculated from : P=I^2*R (See ohm's circle )

Resistor values - the resistor colour

code

1

Ω

is quite small so resistor values are often given in k

Ω

and M

Ω

(why..?).
1 k

Ω

= 1000

Ω

, 1 M

Ω

= 1000000

Ω

.

Resistor values are normally shown using coloured bands.
Each colour represents a number as shown in the table.

Most resistors have 4 bands:

• The first band gives the first digit.
• The second band gives the second digit.
• The third band indicates the number of zeros.
• The fourth band is used to shows the tolerance (precision) of the resistor, this may be ignored for almost all circuits but further details are given below.

This resistor has red (2), violet (7), yellow (4 zeros) and gold bands.
So its value is 270000 Ω = 270 kΩ.
On circuit diagrams the

Ω is usually omitted and the value is written 270K.

Find out how to make your own Resistor Colour Code Calculator

Small value resistors (less than 10 ohm)

The standard colour code cannot show values of less than 10. To show these small values two special colours are used for the third band: gold which means × 0.1 and silver which means × 0.01. The first and second bands represent the digits as normal.

For example:
red, violet, gold bands represent 27 × 0.1 = 2.7Ω
green, blue, silver bands represent 56 × 0.01 = 0.56 Ω

Tolerance of resistors (fourth band of colour code)

The tolerance of a resistor is shown by the fourth band of the colour code. Tolerance is theprecision of the resistor and it is given as a percentage. For example a 390 resistor with a tolerance of ±10% will have a value within 10% of 390Ω, between 390 - 39 = 351Ω and 390 + 39 = 429Ω (39 is 10% of 390).

A special colour code is used for the fourth band tolerance:
silver ±10%, gold ±5%, red ±2%, brown ±1%.
If no fourth band is shown the tolerance is ±20%.

Tolerance may be ignored for almost all circuits because precise resistor values are rarely required.

For more understanding of Resistors color codes , see this video( pling # 3)

Now, you can go to buy some resistors from electronics shop , go now and buy nomber of resistors with various values .

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How to read a Resistor Color Code

in this video, we will discuss how to read a Resistor color code , and how to choose your resistor .

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Resistor Color code

Instructions:

Requirements

• Java is required and a link should appear if you do not already have Java installed. Use this link to get started. With Java installed, the resistor tool should load up automatically.


• Selecting a value
  Click on just about any colored box to change the value for the displayed resistor. Each color table can be used to select a value for the indicated color band.


• Invalid color values
  If you select and invalid set of colors the resistor value and code fields will show Invalid. Note that the valid values table shows all the possible values for the first two bands and changes based on the selected tolerance.


• Common Values
  Click on one of these common resistor values to quickly show the colors for that value.


• Valid Values
  Click on one of the valid values for the first two code digits. This table will help you find the closest valid value when your calculating a resistor for some project.

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Now, We can control

we can conclude all previous by discussing the following :

what is the voltage , what is the current and what is the "Resistors" (our first component ).

But now, we will start to control the voltage and current as we discussed before .

this topic will be divide into two section

1. How to control "voltage" (By Resistors Only) ==> Resistors Series connection

simply, if we have to "Resistors" connected in series (see fig R.1) , each resistance between two nodes ( called "node " in circuits) .

fig R.1

voltage is measured between two points as we know, here we can divide voltage into two components , each resistance have a specific voltages between its terminals . (see fig R.2)

fig R.2

of course , current will not change , here we can change only voltage by changing values or nombers of this resistances .

We will back Sooooooon

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