The temperature coefficient of resistance for a wire is $0.00125\,^oC$. At $300\,K$ its resistance is $1\, ohm$. The temperature at which the resistance becomes $2\, ohm$ is .......... $K$
IIT 1980, Medium
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$\frac{{{\rho _1}}}{{{\rho _2}}} = \frac{{(1 + \alpha {t_1})}}{{(1 + \alpha {t_2})}} \Rightarrow \frac{1}{2} = \frac{{(1 + 0.00125 \times 27)}}{{(1 + 0.00125 \times t)}}$
$ \Rightarrow t = 854\,^oC$ $\Rightarrow T = 1127\,K$
$ \Rightarrow t = 854\,^oC$ $\Rightarrow T = 1127\,K$
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