Question

The resistance of a wire of length 100 cm and 7 x 10${}^{-3}$ cm radius is 6 ohm. Its specific resistance is

• A. $924\times {10}^{-8}\Omega cm$
• B. $92.4\times {10}^{-8}\Omega cm$
• C. $900\times {10}^{-8}\Omega cm$
• D. $224\times {10}^{-8}\Omega cm$

Answer 1

Answer: (A)

$924\times {10}^{-8}\Omega cm$

$R=\frac{\rho L}{A}$

$\Rightarrow 6=\frac{\rho \times 100}{\pi (7\times {10}^{-3}{)}^2}$

$22\times 42\times {10}^{-8}=\rho$

$\rho =924\times {10}^{-8}\Omega cm$