What is electrical resistivity of a material ? State its SI unit and d

1.	What is electrical resistivity of a material ? State its SI unit and define it.
Answer» Solution :It is found that the resistance R of a uniform metallic conductor depends on its length 1, on its area of cross-section A, the nature of its material and TEMPERATURE Precise measurements have shown that at a given temperature, `R PROP l and R prop 1/A` Combining above two relations, `R prop l/A` `:. R =rho l/A` .......(12.6) Where `rho` (rho) is a constant of proportionality and is called the electrical resistivity of the material of the conductor. From equation (12.6) `rho = (RA)/l ` .... ...(12.7) `:.` The SI unit of `rho` `= ("The SI unit of resistance "xx" The SI unit of area of cross - section")/("The SI unit of length")` `=(Omegam^2)/m` `=Omegam` (ohm-metre) In equation (12.7), if A = 1 unit and l = 1 unit, `rho = R`. The electrical resistivity of a material is the resistance of a conductor (of that material) having unit length and unit area of cross-section. [Notes : (1) Resistivity depends on temperature. (2) Resistivity is also called SPECIFIC resistance.]

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