Length of a hollow tube is `5 m`, its outer diameter is `10 cm` and thickness of its wall is `5 mm`. If resistivity of the material of the tube is `1.7 xx 10^(-8) Omega xx m`, then resistance of tube will be

Options

A. `5.6 xx 10^(-5) Omega`
B. `2 xx 10^(-5) Omega`
C. `4 xx 10^(-5) Omega`
D. None of these

Answer

A

Explanation

`l =5m, d = 10 cm, r= 5 xx 10^(-2) m, t = 5 xx 10^(-3) m`
Area of cross section (A) `= 2pir xx t`
`=2pi xx 5 xx 10^(-2) xx 5 xx 10^(-3)`
`= 50 pi xx 10^(-5) m^(2)`
`R = (rho l)/(pir_(1)^(2) - pir_(2)^(2)) = (1.7 xx 10^(-8) xx 5)/((25pi - 20.25pi) xx 10^(-4)) = 5.6 xx 10^(-5) Omega`