Electric Current Through Conductors — Physics STD 11 Science — Question
Maharashtra BoardEnglish MediumSTD 11 SciencePhysicsElectric Current Through Conductors3 Marks
Question
Derive expression for specific resistance of a material.
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Answer
At a particular temperature, the resistance $(R)$ of a conductor of uniform cross section is i. directly proportional to its length (l), i.e., $R \propto I$ $\qquad$ (1) ii. inversely proportional to its area of cross section (A), $R \propto \frac{1}{A}$ From equations (1) and (2), $R =\rho \frac{l}{A}$ where $\rho$ is a constant of proportionality and it is called specific resistance or resistivity of the material of the conductor at a given temperature. iii. Thus, resistivity is given by, $\rho=\frac{R A}{l}$
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