What is Self-Esteem?

Resistor is resistance to the flow of an electric current, with some materials resisting the current flow more than others.

Ohm's Lawstates that when a voltage (V) source is applied between two points in a circuit, an electric current (I) will flow between them, encouraged by the presence of a potential difference between these two points.The amount of electric current flowing is limited by the amount of resistance (R) available.In other words, the voltage encourages the flow of the current (movement of the load), but it is the resistance that discourages it.

We always measure electrical resistance in Ohm, where Ohm is indicated by the Greek letter Omega, Ω.For example: 50Ω, 10kΩ or 4.7MΩ, etc. Conductors (e.g. wires and cables) usually have very low resistance values (less than 0.1Ω), and therefore we can neglect them, as we assume that the wires are zero ohm in circuit analysis calculations.Insulators (e.g. plastic or air) usually have very high resistance values (greater than 50MΩ), so we can also ignore them for circuit analysis, as their values are very high.

However, the electrical resistance between the two points can depend on many factors such as the length of the conductors, the section area, the temperature and the actual material from which they are made.For example, suppose we have a wire part (a conductor) with L length, A section area and R resistance, as shown.

Single Conductor


The electrical resistance of this simple conductor is a function of R, length, L and conductive field, A. Ohm law tells us that for a certain resistance R, the current flowing from the conductor is proportional to the voltage applied: I = V/R.Now let's say that we connect two identical conductors in a series combination, as shown.

Doubling the Length of a Conductor


Here we effectively doubled the total length (2L) of the conductor in a series combination, that is, by connecting them end-to-end, the section area remains exactly the same as the previous one.But in addition to doubling the length, we also doubled the total resistance of the conductor and gave the 2R in 1R + 1R = 2R.

Therefore, we can see that the resistance of the conductor is proportional to its length, that is: R ∝ L .In other words, we expect the electrical resistance of a conductor (or wire) to be proportionally greater, the longer it is.

To force the same current, by doubling the length and therefore the resistance of the conductor (2R), this i must now double a voltage (increase) applied to i = conductor flow (2V) /(2R).Next, let's say that we connect two identical conductors together in parallel combination, as shown.

Doubling the Conductive Area


Here, by connecting the two conductors in a parallel combination, we effectively doubled the total area by giving 2A, while the length of the conductors L remained the same as the original single conductor.But in addition to doubling the field, we have effectively halved the total resistance of the conductor by connecting the two conductors in parallel, and now each half of the current will give 1/2R as it flows through each conductor arm.

Thus, the resistance of the conductor is inversely proportional to the area, that is: R 1/∝ A or R ∝ 1/A.In other words, we expect the electrical resistance of a conductor (or wire) to be proportionally less, the larger the cross-sectional area.

We also need to double the field and therefore halve the total resistance of the conductive branch (1/2R), for the same current, we need only half (reduce) the voltage applied as now for the i to flow through the parallel conductor branch as before I = (1/2V)/(1/2R).

I hope that we can see that the resistance of a conductor is directly proportional to the length (L) of the conductor, that is: R ∝ is inversely proportional to L and its area (A), R ∝ 1/A.Thus, we can say that the resistance is correct:

Resistance Proportionality


But in addition to the length and conductive area, we expect the conductor to depend on the actual material from which electrical resistance is also made, since different conductive materials, copper, silver, aluminum, etc. all have different physical and electrical properties.Thus, we can convert the proportional sign (∝) of the above equation into an equal sign simply by adding a "proportional constant" to the equation above:

Electrical Resistance Equation


Where: Resistance in R ohm (Ω) is the length in L meters (m), the area in square meters (m 2), and the proportion constant ε (the Greek letter "rho") is the self-deprecation where it is known.

Electrical Resistance

The electrical resistance of a particular conductive material is a measure of how strongly it opposes the flow of electric current through the material.Sometimes referred to as "specific electrical resistance", this self-extracting factor allows comparison of resistances at a certain temperature according to the physical characteristics of different types of conductors, regardless of their length or sectional area.Thus, the higher the self-extracting value of ε, the greater the resistance, and vice versa.

For example, when the extractive of a good conductor such as copper is 1.72 x 10-8 ohm meters (or 17.2 nΩm), the extractive of a weak conductor (insulator) such as air can be well above 1.5 x10 14or 150 trillion Ωm.

Materials such as copper and aluminum are known for their low resistance levels, so they allow electric current to flow easily, making these materials ideal for making electrical wires and cables.Silver and gold have very low self-esteem values, but for obvious reasons it is more expensive to convert them into electrical wires.

Then the factors affecting the resistance (R) of a conductor in ohms can be listed as follows:

  • The extractive (ε) of the material from which the conductor is made.
  • Total length of conductor (L).
  • Section area of the conductor (A).
  • The temperature of the conductor.

Özdirenç Question Example 1

If the resistance of copper at 20 o C is 1.72 x 10 -8 Ω meters, calculate the total DC resistance of 2.5 mm 2 copper wire rolls of 100 meters.

Data given: copper's extractive 1.72 x 10 -8 at 20 o C , coil length L = 100m, cross-sectional area of conductor is 2.5 mm 2,which is equivalent to the following section area: A = 2.5 x 10 -6 meters 2 .


We have previously said that the extractive is unit length and electrical resistance per unit conductive section area, so we have shown that the extractive has dimensions of ε ohm meters or Ωm as commonly written.

Electrical Resistance, Rho


Elective Conductivity

Both electrical resistance (R) and self-deprecation (or specific resistance) ε are a function of the physical nature and length (L) of the material used and the physical shape and size expressed by the section area, conductivity or special conductivity is related to the ease of the electric current flowing from a material.

Conductivity (G) is the equivalent of resistance (1/R), whose conductivity unit is siemens (S), and the upside-down ohm symbol is given as mho, ℧.Thus, when the conductivity of a conductor is 1 siemens (1S), its resistance is 1 ohm (1Ω).So if its resistance doubles, the conductivity is halved and vice versa: siemens = 1/ohms or ohms = 1/siemens.

While the resistance of conductors gives the amount of resistance to the flow of electric current, the conductivity of the conductor indicates how easily it allows the electric current to flow.Therefore, metals such as copper, aluminum or silver have very large conductivity values, that is, they are good conductors.

Conductivity is the opposite of resistance to σ (Greek letter sigma).This is 1/ε and measured in siemen/meter (S/m).Since the electrical conductivity σ = 1/ε, the previous expression for electrical resistance, R, can be rewritten as follows:

Electrical Resistance as a Function of Conductivity


Then we can say that conductivity is the efficiency of passing an electric current or signal of a conductor without loss of resistance.Therefore, since a material or conductor with high conductivity is equal to 1 siemens (S) 1Ω -1, it will have a low resistance, and vice versa.

Özdirenç Question Example 2

The cross-sectional area of a cable 20 meters long is 1 mm 2 and its resistance is 5 ohm.Calculate the conductivity of the cable.

The data given is: DC resistance, R = 5 ohm, cable length, L = 20m, and the cross-sectional area of the conductor is 1 mm 2,which is as follows: A = 1 x 10 -6 meters2 .


That's 4 mega-siemens per meter of length.


In this tutorial on the extract, we found that the extractive is the property of a material or conductor that shows how well the material transmits the electric current.We also found that the electrical resistance (R) of a conductor depends not only on the material in which the conductor is made, copper, silver, aluminum, etc., but also on its physical dimensions.

The resistance of a conductor is directly proportional to its length (L) in R ∝ L. Thus, doubling its length will double its resistance, while halving its length will reduce its resistance in half.In addition, the resistance of a conductor is inversely proportional to the cross-section area (A) and R ∝ 1/A.Thus, doubling the section area will reduce its resistance in half, while halving the section area will double its resistance.

We also learned that the conductor (or material) is related to the physical property in which the extractive (symbol: ε) is made and varies from material to material.For example, the extractive of copper is usually given as follows: 1.72 x 10 -8 Ωm.The extractive of a particular material is measured in Ohm-Meters (Ωm) units, which are also affected by temperature.

Depending on the electrical extract value of a particular material, it can be classified as "conductor", "insulator" or "semiconductor". Keep in mind that semiconductors arematerials whose conductivity depends on impurities added to the material.

Resistance is also important in power distribution systems, since the effectiveness of the grounding system for an electrical power and distribution system largely depends on the resistance of soil and soil material at the site of system grounding.

Transmission is the name given to the movement of free electrons in the form of electric current.Conductivity is the opposite of σ self-indivity.This is 1/ε and has siemens divided by s/m unit.Conductivity varies from zero (for a perfect insulator) to infinity (for an excellent conductor).Thus, a superconductor has infinite conductivity and almost zero omic resistance.