If you are learning physics, then you must have gone through the word’s resistance and resistivity. Even if you didn’t come across them, it is still essential to know as they are generally being used somewhere in our day-to-day life. If you are a student studying current and electricity, understanding the terms “resistance” and resistivity” will help you look at more complex physics topics.
What is resistance?
The resistance of a component is a measure of the opposition an electric current experiences when it flows through the element.
Resistance is the opposition offered by the substance to the flow of free electrons. This opposition occurs because atoms and molecules of the substance obstruct the flow of these electrons. Certain substances (metals such as silver, copper, and aluminum) offer very little opposition to the flow of electric current.
It may be noted here that resistance is the electric friction offered by a substance and causes heat production with the flow of electric current. The moving electrons collide with atoms or molecules of the essence—each collision resulting in the liberation of a minute quantity of heat. The SI unit of Resistance an Ohm and is represented by the symbol Ω(omega).
The resistance of metallic conductors, ohmic or non-ohmic, generally increases with increasing temperature. The resistance of a metallic conductor in a circuit can be determined using an ammeter or voltmeter. An increase in the temperature of a metallic conductor causes an increase in its resistance.
It is defined as the resistance of a wire is to be 1 Ohm if a potential difference of one volt across its end causes one ampere current to flow through it. 1 Ω= 1V/1A. Resistance depends on the length and cross-sectional area of the material.
Factors upon which resistance depends.
When electrons flow through a wire, they experience resistance and lose energy. As the electrons flow on the long path, they lose more power. It is observed that total resistance of a wire experimentally:
- It’s directly proportional to its length.
- It is inversely proportional to its area of cross-section. Therefore, thicker wires have less resistance per meter and will cause less energy as heat.
- It depends upon the nature of the material.
- It is directly proportional to the temperature.
- From the first three-point (keeping the temperature constant). The resistance of a conductor R ∝L/A or R= ρ*L/A, where ρ (Greek letter “Rho”). A regular known as resistivity or specific resistance of the material.
What is specific resistance or resistivity?
Resistivity is not the same as resistance. It is a property of the material that is independent of the dimensions of the material.
We have seen above that R= ρ*L/A. If L= 1m, A=1 m2, then R= ρ.
Hence specific resistance of material is the resistance. Offered by 1m length of wire of a material having an area of cross-section of 1m2. The unit of resistivity is the(Ω.m). The resistivity of a substance varies over a wide range.
The resistivity of metals and allows is very small. Therefore, these materials are good conductors of electric current. On the other hand, the resistivity of insulators is extremely large. As a result, these materials hardly conduct any current. There also an intermediate class of materials known as semiconductors. The resistivity of these substances lies between conductors and insulators.
What are resistors?
A resistor is is a conductor in a circuit used to control the current’s size flowing in a course. Resistors can have a resistance that ranges from a few ohms to several millions of ohms. There are two types of resistors, fixed resistors and variable resistors.
A fixed resistor has a resistance of fixed value. Common types of fixed resistors include carbon film resistors and wire-wound resistors. A variable resistor has a resistance that can be varied. It uses to run the amount of current flowing in the circuit.
Let’s look into the bases that differentiate their Difference between resistance and resistivity.
The physical property of a substance that opposes the flow of current(electrons) that called Resistance. However, a physical property of a specific sense with specific dimensions that called Resistivity.
Resistance is directly proportional to the length and temperature of a substance. Hence, it is inversely proportional to the cross-sectional area of the sense. In contrast, resistivity is proportional to the nature and temperature of the specific meaning.
R is the symbol representing resistance, and ρ is the symbol for resistivity.
Resistance calculated from these formulas: R = V/I or R = ρ(L/A) V = Voltage, I = Current, ρ = Resistivity.
Resistivity calculated as: ρ = (R×A)/L where R = Resistance, L= Length, A = Cross-sectional area.
5. SI unit
Ohms is the SI unit of resistance, and Ohms-meter is the SI unit of resistivity.
Scientists have found various places where they can use the properties of resistance and resistivity. However, resistance uses in heaters, sensors, and fuses, etc. Still, resistivity use in tests like quality control tests for calcareous soil.
We hope that you have understood the concept of resistance and resistivity in detail. If you are a student. We wish you luck for your examination. Applying information gained through this blog as you have seen the significant differences between resistance and resistivity. It would help if you kept searching more on the topic of current and electricity.
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