中三物理題~高手入來解釋下~10分

用戶36732

2009-01-11 9:21 pm

1
The mass of two metal blocks A and B is in the ratio of 2:1 and the amount of energy supplied to them is in the ratio of 3:4. If the change of their temperatures are the same, calculate the ratio of their specific capacity.

A 1:2
B 2:1
C 2:3
D 3:2

點解答案係 D?

2
下列各項中, 哪些可增加沸騰中的水的溫度?

(1)將水劇烈地攪拌
(2)提高發熱器的功率
(3)增加水面的氣壓

A只有(1)
B只有(3)
C只有(1)和(2)
D只有(2)和(3)

點解答案係 B?

回答 (1)

天同

2009-01-12 12:29 am

✔ 最佳答案

1. Option D is definitely NOT the correct answer.
Just judging from the given data, block A has more mass than block B, but receives less heat than block B. In order to achieve the same temperature rise, the specific heat capacity of block A must be smaller than block B.
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2. Stirring the water only achieve a uniform mixing of the hot water, thus obtaining a uniform temperature distribution with the water. It has no effect on the boiling point.
Increase the heat supply only shorten the time on reaching boiling point. It also has no effect on the boiling point.
Increase of external pressure, however, increases the boiling point because water molecules need to acquire more kinetic energy (thus a higher temperature is required) in order to escape from the water surface against the increased external pressure.

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