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In a home experiment , Ram brings a new ...

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 kettle

A

`840W`

B

`1W`

C

`100W`

D

`420W`

Text Solution

Verified by Experts

The correct Answer is:
B
Ans (D)
`(DeltaQ)/(t) =(1 xx 4200 xx 2)/(20)J//sec = 420W`
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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 time taken for the water to cool to 40^(@)C . (Approx)

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