A) 6.4 minutes
B) 6.3 minutes
C) 12.6 minutes
D) 12.8 minutes
Correct Answer: B
Solution :
Electric power consumed by kettle \[P=220\times 4\,W\] Heat required \[H=1000\times 1\,(100-20)=1000\times 80\,\,cal\]\[=4200\times 80\,\,J\] \[P=\frac{H}{t}\Rightarrow \,H=P\times t\] \ \[220\times 4\times t=4200\times 80\]Þ \[t=6.3\,\,\]minutes
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