The external diameter of a 5 metre long hollow tube is 10 cm and the thickness of its wall is 5 mm. If the specific resistance of copper be `1.7xx10^(5)` ohm-metre, then determine its resistance.

Options

A. `5.7xx10^(-5)Omega`
B. `2.7xx10^(-5)Omega`
C. `2xx10^(-5)Omega`
D. `5xx10^( -5)Omega`

Answer

A

Explanation

Area of cross section of tube,
`A= pi (r_(2)^(2)-r_(1)^(2))`
`=3.14[(0.05)^(2)-(0.045)^(2)]`
`=14.91xx10^(-4)m^(2)`
Thus, `R=(rho l)/(A)=(1.7xx10^(-8)xx5)/(14.91xx10^(-4))=5.7xx10^(-5)Omega`