# Dimensional formula for electrical resistivity

$(a)\;ML^3T^{-3}I^{-2} \quad (b)\;ML^2T^{-2}I \quad (c)\;ML^3T^{-2}I^{-2} \quad (d)\;ML^3T^{-3}I^{2}$

$R=\large\frac{\rho\; l}{A}$
$P=i^2R$
$R=\large\frac{P}{i^2}$
$\rho=\large\frac{RA}{l}=\frac{ML^2T^{-3}I^{-2}}{L}$
$\;=ML^{-3}T^{-3}I^{-2}$
Hence a is the correct answer.

edited May 30, 2014