Question

Length of a hollow tube is 5m, it’s outer diameter is 10 cm and thickness of it’s wall is 5 mm. If resistivity of the material of the tube is $1.7\times {10}^{-8}\Omega m$ then the resistance of the tube will be

• A. $5.6\times {10}^{-5}\Omega$
• B. $2\times {10}^{-5}\Omega$
• C. $4\times {10}^{-5}\Omega$
• D. None of these

Answer 1

The correct option is A $5.6\times {10}^{-5}\Omega$


By using $R=\rho .\frac{l}{A}$; here $A=\pi (r_2^2-r_1^2)$
Outer radius $=r_2=5cm$
Inner radius $r_1=5-0.5=4.5cm$
So $R=1.7\times {10}^{-8}\times \frac{5}{\pi \left\{\right(5\times {10}^{-2}{)}^2-(4.5\times {10}^{-2}{)}^2\}}=5.6\times {10}^{-5}\Omega$