| Assertion: The resistivity for a substance is its resistance when its is one meter long and its area of cross section is one square meter. |
| Reason: The SI uints of resistivity are ohm metre \[(\Omega \,m)\]and ohm centimeter \[(\Omega \ cm)\]. |
| Read the assertion and reason carefully to mark the correct option out of the options given below: |
A) If both assertion and reason are true and the reason is the correct explanation of the assertion.
B) If both assertion and reason are true but reason is not the correct explanation of the assertion.
C) If assertion is true but reason is false.
D) If the assertion and reason both are false.
E) If assertion is false but reason is true.
Correct Answer: B
Solution :
[b] We know, \[R\propto \frac{l}{A}\]or \[R=\rho \left( \frac{l}{A} \right)\], where proportionality constant \[\rho \]is called resistivity. If \[l=1m\] and \[A=1{{m}^{2}}\], then \[R=\rho \] i.e. Resistance = Resistivity.
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