Question 594: Current Electricity

Question

A certain wire $\mathrm{A}$ has resistance $81 ~\Omega$. The resistance of another wire $\mathrm{B}$ of same material and equal length but of diameter thrice the diameter of A will be :

Accepted Answer

$\mathrm{R=\frac{\rho L}{A}}$
If diameter becomes thrice then cross section area will become 9 times so
$\mathrm{R\propto \frac{1}{A}}$
Resistance will become $\frac{1}{9}$ times
$\mathrm{R'=\frac{81\Omega}{9}=9\Omega}$

Answer

$81 ~\Omega$

Answer

$9 ~\Omega$

Answer

$729 ~\Omega$

Answer

$243 ~\Omega$

Current Electricity

A certain wire \mathrm{A} has resistance 81 ~\Omega. The resistance of another wire \mathrm{B} of same material and equal length but of diameter thrice the diameter of A will be :

Choose the correct answer: