The resistance of platinum wire at 0 ° C is 2Ω and 6 . 8Ω at 80 ° C...

The variation of resistance of a conducting metal with temperature is given by

${R}_{T} = {R}_{0}\left(1 + \alpha\left({T}_{2} - {T}_{1}\right)\right) . . . \left(1\right)$

Substitute the values of the known parameters into equation (1) and solve to calculate the required temperature coefficient.

$\begin{cases}6 . 8Ω & = & 2Ω \times \left(1 + \alpha\left(80 - 0\right) ° C\right) \\ ⇒ & 1 + 80\alpha = 3 . 4 \\ ⇒ & 80\alpha = 2 . 4 \\ ⇒ & \alpha = 3 \times {10}^{- 2}{C}^{- 1}\end{cases}$