Question

A wire 100 cm long and 2 mm diameter has a resistance of 0.07 ohm, its electrical resistivity of the material is:

• A. 2 ohm-m
• B. $1\times {10}^{-6}ohm-m$
• C. $22\times {10}^{-6}ohm-m$
• D. $44\times {10}^{-6}ohm-m$

Answer 1

Answer: (C)

$22\times {10}^{-6}ohm-m$

Given : $R=0.07\Omega$ $l=100$ cm $=1$ m $d=2$ mm $=0.002$ m

Using $R=\rho \frac{l}{\left(\pi /4\right)d^2}$

$\therefore$ $0.07=\rho \frac{1}{\left(\pi /4\right)(0.002{)}^2}$ $⟹$ $\rho =22\times {10}^{-6}$ $\Omega$ m