An electric kettle takes 10 min to bring water from 30 Celsius to its boiling poing 100 celsius . Fing the extra time required to vapourize the half of the boiling water in the kettle . Assume that no heat is lost to the surrounding .
Specific heat capacity of water : 4200
Specitic latent heat of water : 2.268 * 10^6
唔識計heat.....................
2007-09-11 4:25 am
回答 (1)
2007-09-11 5:06 am
✔ 最佳答案
Energy given out by the kettle:E = Pt
E = P ( 10 )( 60 ) = 600P
The energy required to raise the temperature of water from 30*C to 100*C:
E1 = m( 4200 )( 100 - 30 ) = 294000m
As given,
E = E1
600P = 294000m
P = 490m
The energy required to vapourize half of the boiling water:
E2 = ( m / 2 )( 2.268 x 10^6 )
Then,
Pt = ( m / 2 )( 2.268 x 10^6 )
490mt = ( m / 2 )( 2.268 x 10^6 )
t = 38.6 min ( cor. to 3 s.f. )
Hence the extra time required is 38.6 min.
參考: My Phy Knowledge
收錄日期: 2021-04-13 13:25:10
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