A) 6.3 min
B) 8.4 min
C) 12.6mm
D) 4.2 min
Correct Answer: A
Solution :
Key Idea: Heat evolved due to Joule's effect is used up in boiling water. |
As per key idea \[VIt=ms\Delta t\] or \[t=\frac{ms\Delta t}{VI}\] |
Putting under given values |
\[I=4A,V=220\] volt, \[m=1kg,\] |
\[\Delta t={{(100-20)}^{o}}C,s=4200J/k{{g}^{o}}C\] |
\[\therefore \] \[t=\frac{1\times 4200\times 80}{220\times 4}=6.3\min \] |
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