A) \[300{}^\circ C\]
B) \[400{}^\circ C\]
C) \[500{}^\circ C\]
D) \[200{}^\circ C\]
Correct Answer: B
Solution :
[b] Let resistance of bulb filament be\[{{R}_{0}}\]at\[0{}^\circ C,\] then from expression\[R={{R}_{0}}[1+\alpha \Delta \theta ],\]we have |
\[100={{R}_{0}}[1+0.005\times 100]\] ...(i) |
and \[200={{R}_{0}}[1+0.005\times \times ]\] ...(ii) |
where,\[x\]is temperature in\[{}^\circ C\]at which resistance become\[200\,\Omega \]. |
Dividing Eq. (ii) by Eq. (i), we get |
\[\frac{200}{100}=\frac{1+0.005x}{1+0.005\times 100}\] |
\[\Rightarrow \] \[x=400{}^\circ C\] |
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