A theostat has `1000` turn a wire radius `0.4 mm` having resistivity `49xx 10^(-8) Omega m`. The diameter of each turn is `4 cm. What are the maximum value of conductance and conductivity of rheostat wire.

Answer

`24.5 Omega`

Explanation

Here length of wire used , `l = 100 pi D`
`R = (rhol)/(pi r^(2)) = (rho 100 pi D)/(pi r^(2)) = (100 rho D)/(r^(2))`
`= (100 xx (4.9 xx 10^(-8)) xx (5.0xx 10^(-2)))/((0.1 xx 10^(-3))^(2)) = 24.5 Omega`