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We know there are three types of materials; conductors, semiconductors and insulators. Conductors are the materials that can pass electricity through them. In this document, before we learn about electrical resistivity, let us know what is meant by electrical conductivity and its units.
Electrical Conductivity is an intrinsic property of a material which is defined as the measure of the amount of electrical current a material can carry. Electrical conductivity is also known as specific conductance, and the SI unit is Siemens per meter (S/m). It is also defined as the ratio of the current density to the electric field strength. It is represented by the Greek letter σ.
Electrical conductivity is a measure of how readily a material transmits an electrical current.
Electrical resistivity is the reciprocal of electrical conductivity. It is the measure of the ability of a material to oppose the flow of current.
The table below lists the electrical resistivity of several conductors, semiconductors, and insulators.
Materials having electric field and current density will have the following resistivity formula:
Conductors with a uniform cross-section and uniform flow of electric current will have the following resistivity formula:
Following is the unit of resistivity:
Dimension of resistivity M1L3T-3A-2
Following are the factors that determine the resistivity of materials:
Resistors are used in electrical circuits to control or reduce the flow of current in the circuit. Their resistance is indicated by using electronic color codes. Different color bands or rings are marked on these resistors for different values of resistance.
Resistor Colour Code and
Resistor Tolerance explained Highlights of the resistor color-coding are as follows:
Let us take an example to understand resistor color coding.
1. What is the SI unit of electrical resistivity?
SI unit of electrical resistivity is the ohm-meter.
2. What is the relationship between electrical conductivity and electrical resistivity?
The relationship between electrical conductivity and electrical resistivity is
σ = 1/ρ
3. Is rubber a good conductor of electricity?
Rubber cannot pass electricity, hence is not a conductor.
4. Explain the conductance of a semiconductor?
The conducting capacity of semiconductors lies between a conductor and an insulator.
5. Give some examples of good conductors?