A) \[3000{}^\circ C\]
B) \[325{}^\circ C\]
C) \[3025{}^\circ C\]
D) \[300{}^\circ C\]
Correct Answer: C
Solution :
Idea This question is based on the variation of resistance with temperature. Power\[=\frac{{{V}^{2}}}{R}\] Resistance of hot tungsten\[=\frac{{{V}^{2}}}{P}=\frac{200\times 200}{100}\] \[{{R}_{hot}}=400\Omega \] \[{{R}_{cold}}=40\Omega \] Now, \[{{R}_{hot}}={{R}_{cold}}(1+\alpha .\Delta T)\] \[\therefore \]\[\frac{400}{40}=1+\alpha \times \Delta T\] \[\Delta T=\frac{9}{3\times {{10}^{-3}}}=3000{}^\circ C\] \[\therefore \]\[{{t}_{hot}}=3000{}^\circ +25{}^\circ =3025{}^\circ C\] TEST Edge Similar questions in which some resistance value is given at a particular temperature and the value of resistance at other temperature could be asked.
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