A).28 ohm
B).46 ohm
C).71 ohm
D).152 ohm
why the ans. is (c),not (b)???????
更新1:
sorry,可唔可以有會考程度的解答,我唔識calibration formula
Heat of physics(MC)
2007-04-24 4:20 am
The resistance of an alloy wire is 25 ohm when it is placed in a cup of melting ice. At room temperature of 28'C, the resistance is 38 ohm. If the wire is put in boiling water, what will be the resistance?
A).28 ohm
B).46 ohm
C).71 ohm
D).152 ohm
why the ans. is (c),not (b)???????
A).28 ohm
B).46 ohm
C).71 ohm
D).152 ohm
why the ans. is (c),not (b)???????
回答 (2)
2007-04-24 5:17 am
✔ 最佳答案
每℃的resistance = (38-25) / 28
= 0.464ohm
跟住,你係唔係將 0.464 * 100 =46.4ohm 呢?
其實仲要加番25ohm架.
i.e. [(38-25) / 28 ]+ 25
=71.4ohm
明唔明?希望幫到你.
參考: i'm also a 07phy. hkcee candidate
2007-04-24 4:26 am
Let the resistance of the alloy in boiling water be X ohm,
by calibration formula,
( X - 38 ) / (X - 25) = ( 100 - 28 ) / 100
100X - 3800 = 72X - 1800
28X = 2000
X = 71.428571 ... = 71
So the answer is c) 71 ohm
by calibration formula,
( X - 38 ) / (X - 25) = ( 100 - 28 ) / 100
100X - 3800 = 72X - 1800
28X = 2000
X = 71.428571 ... = 71
So the answer is c) 71 ohm
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