1.

In a home experiment , Ram brings a new electric kettle with unknown power rating . He puts `1` litre water in the kettle and switches on . But to his dismay , the temperature becomes constants at `60^(@)C` after some time. The room temperature is `20^(@)C`. Ram gets bored and switches off the kittle . He sees that during first `20`s water cools down by `2^(@)C`. What is the wattage of the kettleA. `840W`B. `1W`C. `100W`D. `420W`

Answer» Correct Answer - B
Ans (D)
`(DeltaQ)/(t) =(1 xx 4200 xx 2)/(20)J//sec = 420W`


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