Gujarat BoardEnglish MediumSTD 12 ScienceChemistryElectrochemistry2 Marks
Question
What is the electric resistance and resistivity ?
✓
Answer
$\rightarrow $ "The electrical resistance of any object is directly proportional to its length. $1$, and inversely proportional to its area of cross section, A."
$\rightarrow R \propto \frac{l}{A}$
$\therefore R =\rho \cdot \frac{l}{A}$
Where, $\rho=$ Resistivity $(Or)$ specfic resistance
$\rightarrow $ The electrical resistance is represented by the symbol $'R\ '$ and it is measured in ohm $(\Omega)$
$\rightarrow $ SI unit is $kgm ^2 / s ^3 \cdot A ^2$
$\rightarrow $ It can be measured with the help of awheatstone bridge.
$\rightarrow $ "The resistivity for a substance is its resistance when it is one metre long and its area of cross section is one $m^2$."
$\therefore \rho= R \left(\frac{ A }{l}\right)$
$\rightarrow $ Its SI units are ohm metre $(\Omega M )$ and quite often its submultiple. ohm centimetre $( \Omega \ cm )$ is also used.
$1 \Omega\ m =100 \ \ \Omega \ cm$ or $1 \Omega \ cm =0.01 \ \Omega \ m$
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.