Solution:
Solution:
Here, $$R_{1}=2.5\,\Omega, T_{1} = 28\,^{\circ}C$$
$$R_{2} = 2.9\,\Omega$$ and $$T_{2} = 100\,^{\circ}C$$
As $$R_{2}= R_{1}\left[1+\alpha\left(T_{2}-T_{1}\right)\right]$$
$$\therefore 2.9 = 2.5\left[1+\alpha\left(100-28\right)\right]$$
$$\frac{2.9}{2.5}-1 = \alpha\left[72\right]$$ or $$\alpha = \frac{1}{72}\times\frac{2.9-2.5}{2.5}$$
$$ = \frac{1}{72}\times\frac{0.4}{2.5}$$
$$ = 2.22\times10^{-3}\,^{\circ}C^{-1}$$
