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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