Question

if the diameter of a finite length conductor reduces to half then its resistance----

Answer 1

answer: if the diameter of a finite length conductor reduces to half then its resistance four times .

explanation : Let length of rod is l, diameter of rod is d and specific resistance is $\rho$.

we know from formula, $R=\rho\frac{l}{\pi d^2/4}$

if l and $\rho$ are constants then, resistance is inversely proportional to square of diameter of rod.

now a/c to question,

rod of a finite length conductor reduces to half. it is clear that question indirectly said “ specific resistance and length of conductor are constants ”

so, resistance will be 1/(1/2)² time of its initial value. i.e., four time of its initial value.