? asked in 科學及數學其他 - 科學 · 1 decade ago

(20pts)F.3 physics-thermometer

Question:

The lengths of the mercury columns of two mercury-in-glass thermometers are the same at 0 。C. However, when they are placed in the same beaker of warm water, the lengths of the mercury columns are different. Suggest two possible reasons.

The first idea that came into my mind was the" different cross-sectional area". However, if the volume of mercury in the bulb is constant, the the lengths of the mercury columns when 0 degree celcius wouldn't be the same. Then the next consideration( i think) is the sensitivity of the two thermometers, which includes 1. narrower tube 2. change of material 3. increase the volume in the bulb. In no. 2, the material is already fixed. And in no. 1 and 3, as i have mentioned before, the change would also affect the reading when the thermometer is placed in the condition of 0 degree celcius. SO, I WAS CONFUSED.

Perhaps the answer to this question is straight forward, but i would sincerely ask help for those who can help me solve this easy F.3 question.

Thanks a lot!!!!

Update:

thanks mate

2 Answers

Rating
  • Chau
    Lv 5
    1 decade ago
    Best Answer

    You said that the material is fixed,but the mercury may have some impurities.Therefore,the material are not fixed.Hence,i will answer the question as shown as follow.

    The material of the mercury are not the same.It cause different sensitivity.The warm water had't been stired so the warm water are not in the same temperture.

    Actually,the volume of the mercury-in-glass thermometers have not be fixed.You may said that the cross-sectional area are not same when the volume of the thin one is low as the same lengths at 0 oC

    Source(s): myself
  • 1 decade ago

    Since all mercury stays in the bulb at 0oC due to contraction,therefore the lengths of the mercury columns are said to be the same (both 0cm)when the temperature is at 0oC.Actually,for mercury in glass thermometer,it is seldom used to measure temeratures lower than 0oC,since the freezing point of mercury is very close to 0oC(about -39oC),so it is meaningless to make the temperature scale below 0oC(That means the temperature scale in mercury in glass therometer is 0oC to 100 above).You ideas are correct:They have different cross-sectional area(larger bore) and the sensitivity due to (1) to (3)to conclude,when these thermometers are placed at 0oC,all mercury contracts and drip back in the bulb ,i.e the liquid level of mercury in the long tube becomes zero.

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