Question

A metallic wier has a resistance of `120 Omega at 20^@C.` Find the temperature at which the resistance of same metallic wire rises ot `240 Omega` where the teperature coefficient of the wire is `2xx10^(-40) C^(-1).`

Answer 1

Given `R_1 = R_(20) = 120 Omega, R_2 = R_1 = 240Omega, t =?, alpha = 2xx10^(-40)C^(-1)`
`t_1 = 20^@C, t_2 = T =?`
Formular used to find the temperature coefficient of
(i) resistance is
(ii) `alpha = (R_2 -R_1)/(R_1(t_2 - t_1)) = (R_T- R_(20))/(R_(20) (T - 20)`
or `2xx10^(-4) = (240 - 120)/(120(T - 20))`
or `T-20 =(120)/(120xx2xx10^(-4))`
or `T = (1)/(2xx10^(-4) + 20 = 0.5xx10^4 + 20) = 5020^@C`