What is resistivity of a material?
The electrical resistivity of a material is also known as its specific electrical resistance. It is a measure of how strongly a material opposes the flow of electric current. A definition of resistivity is the electrical resistance per unit length and per unit of cross-sectional area.
Electrical or thermal condutivity, resistivity, density and melting point
|TIBTECH||Electrical conductivity (10.E6 Siemens/m)||Electrical resistivity (10.E-8 Ohm.m)|
- Resistance of a conductor is the obstruction offered by the conductor in the flow of current through it. It is measured by the potential difference needed across the conductor to flow one ampere current through it. The resistance of a conductor depends upon its material, temperature, length and area of cross section.
- The most conductive of all metals are silver, copper and gold in that order. Silver is also the most thermally conductive element, and the most light reflecting element. Silver also has the unusual property that the tarnish that forms on silver is still highly electrically conductive.
- Brass is only 28% as conductive as copper. Some bronzes are as low as 7% as conductive as copper! Copper is the standard by which electrical materials are rated and conductivity ratings are expressed as a relative measurement to copper. The higher the % IACS, the more conductive the material is.
Aluminum is lighter than copper. Aluminum has a resistivity varying from 2.65 to 2.82 × 10−8 Ω · m. Combined with it's light weight and alloyed with some other metals to make it stronger, aluminum is ideal for electrical cables.
- Molar conductivity is defined as the conductivity of an electrolyte solution divided by the molar concentration of the electrolyte, and so measures the efficiency with which a given electrolyte conducts electricity in solution. Its units are siemens per meter per molarity, or siemens meter-squared per mole.
- An ohmmeter is an electrical instrument that measures electrical resistance, the opposition to an electric current. Megohmmeters (also a trademarked device Megger) measure large values of resistance. The unit of measurement for resistance is ohms (Ω).
- Resitivity is a measure of the resistance to electrical conduction for a given size of material. Its opposite is electrial conductivity (=1/resistivity). The ease with which a material conducts heat is measured by thermal conductivity. As a first estimate, good electrical conductors are also good thermal conductors.
As the graph shows, the resistivity of a substance is very much dependent on temperature. For most conductors, resistivity increases with rising temperature. At 20 °C, the resistivity of gold is approximately 2.44 × 10−8 ohm-m and steadily rises with increasing temperature.
- Electrical or thermal condutivity, resistivity, density and melting point
TIBTECH Electrical conductivity (10.E6 Siemens/m) Electrical resistivity (10.E-8 Ohm.m) Silver 62,1 1,6 copper 58,5 1,7 Gold 44,2 2,3 Aluminium 36,9 2,7
- Surely, upon an increase in temperature, the atoms within the thermistor would vibrate with more energy and therefore more vigorously, hence making the electrons flowing through the electric circuit more likely to collide with one of the atoms, so increasing resistance.
- We have also learnt that the resistivity (symbol: ρ) of the conductor (or material) relates to the physical property from which it is made and varies from material to material. For example, the resistivity of copper is generally given as: 1.72 x 10-8 Ω.m.
Updated: 16th October 2019