Answer
$T=1.8\times10^3 C^\circ$
Work Step by Step
$R=\frac{V}{i}=\frac{2.9}{0.3}=9.7 ohm$
For tungsten, the temperature coefficient is $\alpha=4.5\times10^{-3}$
We know that
$T-T_\circ=\frac{R-R_\circ}{\alpha R_\circ}$
$T=T_\circ+ \frac{R-R_\circ}{\alpha R_\circ}$
We plug in the known values to obtain:
$T=20^\circ+ \frac{9.67-1.1}{(4.5\times10^{-3})(1.1)}$
$T=1751 C^\circ$
$T=1.8\times10^3 C^\circ$
