What Is The Difference Between Resistance And Resistivity?
We explain that what is the difference between resistance and resistivity. with definitions, examples, and in tabular form to better understand the concepts.
Resistance is defined as the property of a conductor to resist the flow of current. It is also defined as the ratio of the voltage applied to the current flowing through it. The resistance of a conductor depends on its length, its cross-section, and the properties of the material from which the conductor is made. For conductors, the resistance is directly proportional to the length of the conductor and inversely proportional to its cross-section.
Resistivity is defined as the resistance exerted by a material per unit length per unit cross-section. The SI unit of resistivity is the ohmmeter. The resistivity increases proportionally to the temperature. The specific resistance of conductors is lower than that of insulators. It can therefore be expressed as follows:
Conductor resistivity < alloy resistivity < insulation resistivity.
What is the Resistance?
The term resistance is used in conductors and acts as an obstacle in the flow of current or free electrons that are present in a conductor. The resistance (R) in a conductor is generally the relationship between the potential difference (V) of the current (I) that crosses it. It is written mathematically as R = V / I or R = ρ (L / A).
Where, l – length of the conductor, a – cross-sectional area of the conductor, ρ – resistivity of the material. When the flow of charges occurs in a conductor, the flow of electrical current begins to travel. When a current flows through a cable, it looks like water flowing in a water pipe, and when the voltage drops in the cable it is similar to the pressure drop that drives the water in the pipe.
For example, consider a flow of electric current in a uniform piece of cylindrical wire as a result of the potential difference. When this flow of electrons occurs in an electrical wire, the atoms present in the wire vibrate their nuclei and very repeatedly knock the electrons out of their flow path and produce heat and this opposition results in the appearance of resistance. The longer the cylinder, the additional collisions of charges with its atoms will occur.
The unit of resistance is measured in ohms and is generally represented as Ω in kΩ. The resistance is directly proportional to the diameter, so the greater the width of the cylinder, the greater the current it can take. Different materials have different resistance to the movement of charge in the conductor.
The resistance through a wire rope is directly proportional to the length and inversely related to the cross-section of a constant wire rope.
Factors affecting resistance
- Cable resistance generally increases with increasing conductor length.
- The resistance is inversely proportional to the cross-sectional area of the metallic conductor.
- Resistors rest on the material of the wire.
- The resistance of the material usually depends on its temperature.
- Small wires tend to have a lower resistance; Large wires have great strength.
- Various materials develop superconductors when these materials drop below a critical temperature that offers zero resistance to current flow in the conductor.
What is resistivity?
The term resistivity is a particular resistance that has specific dimensions. The two particular situations and when they are associated, form a resistivity equation that is like ρ = (R × A) / L
Where ρ is the constant (known as the Greek letter “rho”) called the resistivity of the material, l – length of the conductor, a – cross-sectional area of the conductor, and R – resistance of the material. Resistivity is usually a property of a specific material and is independent of dimensions, but depends on the temperature and the material of the conductor.
Resistivity is usually the ratio of the electric field strength (E) to the current density (J) present at a particular temperature, written as ρ = E / J. The resistivity unit is usually measured in ohmmeters (Ω m) and R symbolizes it. The resistivity through a metal wire is directly proportional to the temperature of the material and is independent of dimensions.
Main difference
The main difference between resistance and resistivity is that resistance opposes the flow of current and free electrons, while resistivity describes the resistance of the specific material that has a particular dimension.
Resistance vs resistivity
Resistance is a specific property of a material that creates obstacles in the flow of current; conversely, resistivity is a particular resistance that has specific dimensions. Resistance in a conductor is generally the ratio of the potential difference of the current through it, while resistivity is usually the ratio of the electric field intensity to the current density present at a particular temperature. The unit of resistance is measured in ohms (Ω), while the unit of resistivity is generally measured in ohmmeters (Ω m). The symbol for resistance is R; instead, the symbol for resistivity is ρ.
The resistance is considered as a property of a specific object and will be determined by the temperature, the material of the object, together with its dimensions (directly proportional to the length, inversely related to the cross section in a constant metal wire); On the other hand, resistivity is usually a property of a specific material and is independent of dimensions, but depends on the temperature and the material of the conductor. The formula for resistance is written as R = V / I or R = ρ (L / A); On the other hand, the formula for resistivity is written as ρ = (R × A) / L.
Resistance property applications in daily life are used in various places and things like fuses, heaters, sensors, etc .; on the other hand, electrical resistivity measurement applications are involved in calcareous soils and a quality control test. The resistance is always connected to the specific conductor; On the other hand, resistivity is usually related to the conductor material.
What is the difference between resistance and resistivity?
Comparison Table
Resistance | Resistivity |
The property of a substance that offers opposition to the flow of current is known as resistance. | The resistivity of 1 m ^{3} of a substance is equal to the specific resistance. |
Ratio of | |
The relationship between the potential difference that crosses it and the current that passes | The relationship between the intensity of the electric field and the current density present at a particular temperature. |
Unit | |
The unit of resistance is ohms (Ω) | The unit of resistivity is ohms (Ω m) |
Symbols | |
The symbol for resistance is R | The symbol for resistivity is ρ |
Considered as | |
Considered as a property of a specific object and determined by temperature, the object’s material, along with its dimensions. | Usually a property of a specific material. |
Temperature dependence | |
It depends on the temperature | It depends on the temperature and the material of the conductor. |
Dimensional dependency | |
It depends on the dimension | It does not depend on the dimension |
Length and cross-sectional area dependency | |
Directly proportional to length, inversely related to cross section in a constant metal wire | It does not depend on the length and cross-sectional area of the conductor. |
Formula | |
R = V / I or R = ρ (L / A) | ρ = (R × A) / L |
Connection with conductor | |
Always connected to the specific driver | Generally linked to the conductor material. |
Applications | |
Resistance property applications in daily life are used in various places and things like fuses, heaters, sensors, etc. | Applications of electrical resistivity measurement are involved in calcareous soils and a quality control test. |
Key differences between resistance and resistivity
- One property that creates obstacles in the flow of free electrons and current is usually resistance; conversely, a particular resistance having specific dimensions is given by resistivity.
- Resistance is tied to the specific conductor; on the other hand, resistivity is related to the conductor material.
- In a conductor, resistance is the ratio of the potential difference through which current passes, while resistivity is usually the ratio of electric field strength to current density that occurs at a specific temperature.
- The unit of resistance is ohms (Ω), while the unit f of resistivity is commonly ohmmeters (Ω m).
- The symbol for resistance is R; on the contrary, the symbol for resistivity is ρ.
- Resistance is directly proportional to length and inversely related to cross section in a constant metal wire; on the other hand, the resistivity depends on the temperature of the metal wire, but it is independent of the dimensions.
- Resistance is determined by the temperature, the material of the object, along with its dimensions and is considered as a property of a specific object; on the contrary, resistivity is normally a specific property of a specific material.
- The formula for resistance is written as R = V / I or R = ρ (L / A); On the other hand, the formula for resistivity is written as ρ = (R × A) / L.
- The applications of the resistor in daily life is that it is used in various places and things like fuses, heaters, sensors, etc .; on the other hand, the applications of electrical resistivity are that it intervenes in calcareous soils and a quality control test.
Conclusion what is the difference between resistance and resistivity
The above discussion concludes that resistance opposes the flow of current and free electrons and depends directly on the dimension and cross section of the area or length, while resistivity is the resistance of the specific material that has a particular dimension but independent of the dimension , depending on the temperature.
Resistance and Temperature
Since the resistance in a material depends on the resistivity, we have:
Thermal coefficient values at a temperature of 20 ° and in units of K⁻¹
Steel | 5.0 x 10 ^{-3} |
Aluminum | 3.9 x 10 ^{-3} |
Coal | -0.5 x 10 ^{-3} |
Copper | 3.9 x 10 ^{-3} |
Germanium | -4.8 x 10 ^{-2} |
Mercury | 0.9 x 10 ^{-3} |
Silver | 3.8 x 10 ^{-3} |
Tungsten | 4.5 x 10 ^{-3} |
The temperature coefficient, usually symbolized as α, is an intensive property of materials that quantifies the relationship between the variation of the physical property of a material and the change in temperature. Therefore, it is the relative change of a physical property when the temperature is changed by 1 K. This coefficient is expressed according to the International System of Units in 1 / K. Its mathematical expression takes the form:
In this equation
R (T) = resultant resistance to Tf
Ro = Initial resistance to To
α = Thermal coefficient
ΔT = Temperature variation
OHM’S LAW what is the difference between resistance and resistivity
This law relates the three most important variables in electronics, such as current intensity, voltage and resistance. This law is named after the German physicist Georg Ohm , who in a treatise published in 1827, found values of voltage and current that passed through simple electrical circuits that contained a large number of wires. He presented an equation a bit more complex than the one mentioned above to explain his experimental results. .
Where:
V = is the potential or potential difference
I = is the current intensity
R = resistance
The resistance of a material does not depend on the potential difference, nor on the current intensity, but on geometric aspects such as length and cross section, and on the microscopic characteristics of the material, which is given by resistivity.
There are materials in which the ratio between V / I is not a constant, these are called non-ohmic materials. On the other hand, in those that if it is fulfilled, it is said that they are ohmic materials .
Super conductivitywhat is the difference between resistance and resistivity
Superconductivity is called the intrinsic ability of certain materials to conduct electrical current without resistance or loss of energy under certain conditions.
The electrical resistivity of a metallic conductor gradually decreases as the temperature is reduced. However, in ordinary conductors, such as copper and silver, impurities and other defects produce a limit value. Even near absolute zero a copper sample shows non-zero resistance. The resistance of a superconductor, on the other hand, drops sharply to zero when the material cools below its critical temperature . An electric current flowing in a superconducting wire spiral can persist indefinitely without a power source. Like ferromagnetism and atomic spectral lines, superconductivity is a phenomenon of quantum mechanics.
Superconductivity occurs in a wide variety of materials, including simple elements such as tin and aluminum, various metal alloys, and some heavily doped semiconductors. Superconductivity does not normally occur in noble metals such as copper and silver, nor in most ferromagnetic metals. But in certain cases, gold is classified as a superconductor; for its functions and the mechanisms applied.
Difference Between Resistance and Resistivity
Sl. No. | Differentiating Property | Resistance | Resistivity |
1 | Definition | Resistance is the physical property of a substance because of which it opposes the flow of current i.e. electrons. | Resistivity is the physical property of a particular substance which is having particular dimensions. |
2 | Proportionality | Resistance is directly proportional to the length and temperature while it is inversely proportional to the cross-sectional area of the material. | Resistance is only proportional to the temperature of the conductor. It also depends on the nature of the material of the conductor. |
3 | Symbol | R | ρ |
4 | Formula | R = V/I or, R = ρ(L/A) V = Voltage, I = Current, ρ = Resistivity | ρ = (R×A)/L R = Resistance, L= Length, A = Cross-sectional area |
5 | SI Units | The SI unit of resistance is ohm | The SI unit of resistivity is an ohm-meter. |
6 | Applications | The property of resistance is used in several places like heaters, fuses, sensors, etc. | Electrical resistivity measurement is used as a quality control test for calcareous soil. |