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標題:

Heat of physics(MC)

發問:

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)??????? 更新: sorry,可唔可以有會考程度的解答,我唔識calibration formula

• F.3 Chemistry@1@
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• $50新加坡幣=---HKD

• F.3 Chemistry@1@
• log√50-log5
• $50新加坡幣=---HKD

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最佳解答:

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.

其他解答:

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