1.How long does a 500-W rice cooker need to cook a pot of rice if 1 MJ of
energy has to be supplied?
解埋個答案點計出來
2.Two electric kettles(A and B)of different powers.
Electric kettle A (Power=1500W)
Electric kettle B (Power=2000W)
The cost of boiling water is determined by the energy consumed.Will the kettles cost the same or differently for boiling the same volune of water?Why?
就依兩題唔識...幫幫手...>.<
幫我解答幾條physics問題....
2008-11-01 11:19 pm
回答 (2)
2008-11-02 12:08 am
✔ 最佳答案
1.P = 500 W
E = 1 MJ = 1 x 106 J
E = Pt
1 x 106 = 500t
Time required t = 2000 s
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2.
The cost will be the same. (Assume that the heat loss to the surroundings when using kettle A is equal to that when using kettle B.)
To boil the same amount of water at the same initial temperature, the same amount of energy is needed. Since kettle A and kettle B give the same amount of energy to boil the same amount of water, the kettles thus cost the same.
Although kettle B has a lower power rating than kettle A, kettle B needs a longer time to boil the water and thus the energy consumed of B is equal to that of A.
=
2009-10-26 8:41 pm
Kettle A(1500W) Kettle B(2000W),
kettle B has a lower power rating than kettle A?
是不是搞錯了???
kettle B has a lower power rating than kettle A?
是不是搞錯了???
收錄日期: 2021-04-25 19:46:42
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