The primary difference between resistance and resistivity is that the resistance of a material increases as its length and temperature rise, while it decreases as the cross-sectional area of the material grows. While resistivity is influenced primarily by the inherent characteristics and temperature of the material.
What Is Resistance?
Resistance in an electrical circuit is the opposition to the flow of current. It’s quantified in ohms (Ω), represented by the Greek letter omega, and it’s named after Georg Simon Ohm, a German physicist known for his work on the relationship between voltage, current, and resistance, which resulted in Ohm’s Law.
All materials can hinder current flow to varying extents and can be categorized into two main groups:
Conductors:
These materials allow electrons to move with minimal resistance. Notable examples include silver, copper, gold, and aluminum.
Insulators:
These materials impede electron flow by offering high resistance. Common examples encompass rubber, paper, glass, wood, and plastic.
What Is Resistivity?
Resistivity is an inherent property that characterizes a material’s resistance to the flow of electric current, and it is primarily influenced by factors like temperature and potentially other parameters such as pressure. On the other hand, the resistance of a specific piece of material depends not only on its resistivity but also on its physical dimensions, including cross-sectional area (A) and length (L). This relationship can be mathematically expressed as
R = ρL / A
The unit of resistivity is ohm meter (Ωm), while electrical conductivity, denoted by σ (sigma), is the inverse of resistivity and is expressed in siemens per meter (S/m-1).
Resistance vs Resistivity
The key difference between resistance and resistivity is given below:
| 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 ohm-metre. |
| 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. |