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Updated on 02nd May, 2023 , 3 min read
The unit of specific resistance, also known as resistivity, is an essential concept in electrical engineering and physics. It refers to the inherent resistance of a material to the flow of electric current. This article will provide a detailed overview of the unit of specific resistance, including its definition, formula, units, and examples.
Specific resistance, denoted by the Greek letter ρ (rho), is a measure of the resistance of a material to the flow of electric current. It is defined as the resistance of a wire with a unit length and a unit cross-sectional area. In other words, specific resistance is the resistance per unit length and unit cross-sectional area of a material.
The specific resistance of a material is dependent on several factors, including the material's composition, temperature, and impurities. The resistivity of a material is usually expressed in units of ohm-meters (Ωm).
The formula for specific resistance is given as:
ρ = RA/L
Where:
ρ: Specific resistance (Ωm)
R: Resistance of the wire (Ω)
A: Cross-sectional area of the wire (m²)
L: Length of the wire (m)
From the formula, we can see that specific resistance is directly proportional to the resistance of the wire and the length of the wire. It is inversely proportional to the cross-sectional area of the wire.
From the specific Resistance Formula:
Unit of ρ=Unit of R×Unit of A / Unit of L
Electric resistivity, which is also referred to as specific electrical resistance, is a characteristic of a material that indicates its ability to impede the flow of electric current. The symbol used to represent it is ρ, and its unit of measurement is ohm-meter in the International System of Units (SI).
The resistance encountered by air flowing through the respiratory tract during inhalation and exhalation is known as "airway resistance." This can be expressed using a formula analogous to Ohm's law:
RAW = ΔP/V
Where,
Copper has a specific resistance of 1.68 x 10-8Ω.m (20oC). This means that at a temperature of 20oC, the resistance between two opposite surfaces of a copper cube of side 1 m is 1.68 x 10-8 Ω.
The table below shows the conversion factors between different units of specific resistance.
Unit |
Conversion Factor |
1 Ωm |
100 Ωcm |
1 Ωm |
39.37 Ωin |
1 Ωcm |
0.01 Ωm |
1 Ωcm |
0.3937 Ωin |
1 Ωin |
0.0254 Ωm |
1 Ωin |
2.54 Ωcm |
The specific resistance of various other materials are as follows –
Material |
Resistivity in Ohm meter (Ωm) |
Silver |
1.59 x 10-8 |
Copper |
1.68 x 10-8 |
Iron |
9.70 x 10-8 |
Gold |
2.44 x 10-8 |
Platinum |
1.06 x 10-7 |
Zinc |
5.90 x 10-8 |
Tin |
1.09 x 10-8 |
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By - Nikita Parmar 2024-09-06 10:59:22 , 6 min readSpecific resistance, also known as electrical resistivity, is the measure of a material’s ability to resist the flow of electric current. It is measured in units of ohm-meter (Ωm). Specific resistance is measured by applying a voltage across the material and measuring the resulting current. The resistance can then be calculated using Ohm’s law.
The formula for specific resistance is ρ = RA/L, where ρ is the specific resistance, R is the resistance of the material, A is the cross-sectional area of the material, and L is the length of the material.
Resistance is the measure of how much a material resists the flow of electric current, while specific resistance is the measure of a material’s ability to resist the flow of electric current per unit length and per unit cross-sectional area.
The SI unit of specific resistance is ohm-meter (Ωm).
The unit of conductivity is siemens per meter (S/m), and it is the reciprocal of specific resistance. Conductivity and specific resistance are related by the equation σ = 1/ρ, where σ is the conductivity.
The specific resistance of copper is 1.68 x 10-8 Ω.m at 20°C. Copper is a highly conductive material, which means it has a low specific resistance. This property makes it an ideal material for use in electrical wiring and circuits.
Specific resistance and resistivity are the same thing. The term "specific resistance" is more commonly used in the electrical engineering field, while "resistivity" is more commonly used in the physics and materials science fields.
The specific resistance of air is extremely high, approximately 1.3 x 1016 Ω.m. This high resistance makes air an excellent insulator, which is why it is used in electrical applications to prevent electrical current from flowing.
The specific resistance of a superconductor is zero at temperatures below a critical temperature. This property makes superconductors highly desirable for use in electrical applications because they can conduct electricity with zero resistance, resulting in highly efficient and cost-effective electrical systems.
In general, the specific resistance of a material increases as its temperature increases. This relationship is known as the temperature coefficient of resistance and is an important consideration in the design and operation of electrical systems.