# What is Specific Resistance : Formula and Its Units

The resistivity otherwise specific resistance is the resistance in ohms recommend through a material that has a unit volume to the current supply. Resistivity is the mutual of conductivity. A material that has resistivity high, then the conductivity will below. Therefore, an exact resistance of a material is the resistance of a unit volume of that substance. There are many materials available that depend on the resistance in ohms of a material volume This article discusses an overview of this resistance and its formula.

## What is Specific Resistance?

Specific resistance is the resistance accessible for each unit length as well as unit cross-sectional area once the recognized quantity of voltage is applied. Mathematically** specific resistance formula** is represented like the following.

**ρ = RA/L**

Where,

‘⍴’ is a specific-resistance

‘R’ is the resistance

‘A’ is the cross-sectional area

‘L’ is the material’s length

The **unit of specific resistance** is ohm meter or Ωm

This is common for specific conductance, and it can be defined as a calculation of the ability of a substance to conduct electrical energy. The specific conductance can be denoted with ‘k’. It can also refer to specific electric or airway resistance

### Materials at 20^{o}C

The resistance of different substances at 20^{o}C is listed below.

- For material Nichrome, the resistance is 675 ohm-circular mil/ft and 112.2 micro ohm-cm
- For material Nichrome V, the resistance is 650 ohm-circular mil/ft and 108.1 micro ohm-cm
- For material Manganin, the resistance is 290 ohm-circular mil/ft and 48.21 micro ohm-cm
- For material Constantan, the resistance is 272.97 ohm-circular mil/ft and 45.38 micro ohm-cm
- For material Steel, the resistance is 100 ohm-circular mil/ft and 16.62 micro ohm-circular
- For material Platinum, the resistance is 63.16 ohm-circular mil/ft and 10.5 micro ohm-cm
- For material Iron, the resistance is 57.81 ohm-circular mil/ft and 9.61 micro ohm-cm
- For material Nickel, the resistance is 41.69 ohm-circular mil/ft and 6.93 micro ohm-cm
- For material Zinc, the resistance is 35.49 ohm-circular mil/ft and 5.90 micro ohm-cm
- For material Molybdenum, the resistance is 32.12 ohm-circular mil/ft and 5.34 micro ohm-cm
- For material Tungsten, the resistance is 31.76 ohm-circular mil/ft and 5.28 micro ohm-cm
- For material Aluminum, the resistance is 15.94 ohm-circular mil/ft and 2.650 micro ohm-cm
- For material Gold, the resistance is 13.32 ohm-circular mil/ft and 2.214 micro ohm-cm
- For material Copper, the resistance is 10.09 ohm-circular mil/ft and 1.678 micro ohm-cm
- For material Silver, the resistance is 9.546 ohm-circular mil/ft and 1.587 micro ohm-cm

The specific electrical resistance can also be called electric resistivity and it is the property of a substance that defines a substance that opposes the flow of current very strongly.

### What is Airway Resistance?

Airway resistance is the topic of respiratory physiology. It can be defined as the resistance of the respiratory region airflows through inhaling & exhaling. This formula is related to Ohm’s law which is shown below.

**R _{AW}=ΔP/V**

Where,

**ΔP = P _{ATM}−P_{A} R_{AW }= P_{ATM}−P_{AV}˙**

Where,

R_{AW} is airway resistance

ΔP is pressure disparity driving airflow

P_{ATM} is the pressure of atmospheric

P_{A} is the pressure of alveolar

V is the volumetric airflow

The **specific resistance of copper** is a good conductor at 1.72 x 10-8 ohm meter as well as the specific resistivity of air is a poor conductor at1.5 x 1014 ohm meter.

Thus, the specific resistance of a conductor is the unit length & cross-section area of the conductor’s resistance. The property of a substance is when resistance is not available. Once the **specific resistance of a conductor increases with** long length then the resistance will be decreased through the cross-section area. Here is a question for you, what is the specific-resistance of copper?