A) \[300{}^\circ C\]
B) \[400{}^\circ C\]
C) \[500{}^\circ C\]
D) \[200{}^\circ C\]
Correct Answer: B
Solution :
Let resistance of bulb filament is \[{{R}_{0}}\]at\[0{{\,}^{o}}C\] then from expression \[R={{R}_{0}}[1+\alpha \,\Delta \theta ]\] we have, \[100={{R}_{0}}[1+0.005\times 100]\] and \[200={{R}_{0}}[1+0.005\times x]\] where\[x\]is temperature in\[{{\,}^{o}}C\]at which resistance becomes\[200\,\Omega .\] Dividing the above two equations, we have \[\frac{200}{100}=\frac{1+0.005x}{1+0.005\times 100}\] \[\Rightarrow \] \[x=400{{\,}^{o}}C\]You need to login to perform this action.
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